I regret to have to announce that the list of Fellows of this Society deceased since the last Anniversary contains many distinguished names. In most cases their distinction has been won in fields not purely geological; but in the Rev. S. W. King, Geology, and especially Quaternary Geology, has lost a zealous and able cultivator, and the Society a Member of great accomplishments and very versatile abilities. Continued illness prevented him from publishing the results of his labours; but his fossils, collected with the utmost care and accompanied by valuable notes, have enabled Dr. Falconer and Professor Heer to give an adequate account of the animals which lived upon the preglacial continent and of the vegetation which clothed its surface.1
Samuel William King, born September 20, 1821, was the eldest son of the late Rev. William Hutchinson King, formerly Vicar of Nuneaton. At an early age he showed a taste for scientific studies. While a mere boy, from fourteen to sixteen years old, he kept a journal in which astronomical observations and dissections of insects were noted down. Some of his papers were published at the time in the 'Zoologist' As he grew older he turned his attention also to Archaeology and Architecture. He entered at St. Catherine's College, Cambridge, and took the degree of B.A. in 1844, and that of M.A. in 1847. In 1849 he married Emma, daughter of the late John Fort, Esq., M.P., and in 1851 was presented to the Rectory of Saxlingham, Norfolk, where he devoted himself with unflagging  energy to his parochial work and to the study of the antiquities and natural history of the country.
He travelled much, note- and sketch-book in hand. In 1849 and 1850 he visited Switzerland, Italy, Sicily, the Grecian Archipelago, Constantinople and Asia Minor. In 1855 he explored the little-known valleys between Monte Rosa and Mont Blanc; and subsequently published 'The Italian Valleys of the Pennine Alps,' a work that is of very high value, from the rare combination of literary ability with great powers of observation and artistic skill which it manifests. Subsequently he became a Fellow of the Society of Antiquaries and of the Royal Geographical Society. In 1855 he communicated to the Norfolk and Norwich Archaeological Society a paper on the "Examination of an Ancient Cemetery at Hempnall," and in 1859 a second on a "Roman Kiln and Urns found at Hedenham."
On his return, in 1859, from his favourite Pennine valleys and the battle-fields of Solferino and Magenta, his attention was especially directed to the Norfolk Forest-bed by a visit to Cromer with Sir Charles Lyell, Dr. Hooker, and the Rev. John Gunn. From that time he devoted himself to the study of the preglacial beds of Norfolk, and to the accumulation of the fossils that now form the King Collection, which derives a peculiar value from the careful notes of the stratigraphical position of each specimen.
In 1860 he became a Fellow of the Geological Society. In 1864 he was so seriously affected by overwork that he was sent abroad by his medical advisers to seek the rest of mind which he could not obtain in England; but he merely exchanged one field of mental activity for another. On his return through France, after visiting Spain and Majorca, he reopened the famous Cave of Aurignac, and discovered a large number of bones which proved that the cave was open in prehistoric times. A full statement of the bearing of this discovery upon the value of the evidence afforded by the cave, accompanied by the most careful plans and sections, would have been published, had not Mr. King's increasing illness forbidden work of any kind. After his return to England he gradually became worse, until in 1867 he resolved to winter in Algiers, and to give up his favourite pursuits and deeply cherished schemes of work. Thence he travelled to Switzerland, and, daily becoming weaker, he died on the 8th of July, 1868, at Pontresina, in the Engadine, in full possession of all his faculties.
One of Mr. King's last expressed wishes was that his collection, containing all Professor Heer's type specimens of preglacial vegetation, and a large number of Dr. Falconer's type-specimens of Mammals, should be presented to some museum where it might be used for the advancement of the science he loved so well. Accordingly it has found a resting-place in the Museum of Practical Geology in Jermyn Street.
Quaternary Geology has suffered additional losses among our Foreign Members in M. Boucher de Perthes and M. Morlot, whose names will be always honourably associated with that revival of scientific inquiry into the antiquity of man of which this generation has been witness.
M. Jacques Boucher de Crévecur de Perthes, who died in August last, was born in the year 1789, at the commencement of that great era of change which divides modern France from old France. He could hardly recollect the Terror; but the Directory, the Consulate, the Empire, the Restoration, the second Republic, and the second Empire, all had swept before him.
Possessed of an independent fortune, of considerable and varied powers and wide sympathies, M. Boucher de Perthes early resigned an official appointment in order to devote the long remainder of a healthy and vigorous life to travel, to literature, to archæology, and to science. His industry was exemplary, his enthusiasm boundless, his imagination fully equal to all demands made upon it. Hence it is no wonder that his fertile pen poured forth travels, political speculations, and a very readable novelthat he occupied himself with the past of man, and even with the future of woman. But he is most widely known by the great stimulus which his 'Antiquités Celtiques et Antédiluviennes,' published in 1849, gave to the study of the evidence of the antiquity of man which is afforded by the worked implements found imbedded in the same deposits with extinct animals.
The geologists of his own country treated M. Boucher de Perthes's work with indifference and neglect; and no doubt popular historians of science, judging after the event, will hereafter visit them with reprobation for their blindness and their prejudices. But just and critical students of the 'Antiquites' will, I think, be able completely to comprehend, and largely to justify, the course taken by the French geologists. Columbus discovered the new world; and great is his fame for that achievement, history, like some other great powers always paying upon results: but those who will look carefully into the matter will find that most of his reasons for believing in the  existence of the new land which he discovered were either insufficient or erroneous, and might well fail to carry conviction to the minds of the much-abused kings and ministers who so long withheld their help to his great enterprise.
And I venture to doubt whether, if any cautious person were now to read the 'Antiquites Celtiques,' he would rise from its perusal with the feeling that the author's case had been even approximately made outwhether, perhaps, he would not rather be prejudiced against it. Eminently generous, truthful, hearty, and enthusiastic, Boucher de Perthes paid for these virtues by a certain facility of belief, which is as terrible a drawback to scientific weight as it is advantageous in the struggle against neglect and adverse criticism when a man happens to have laid hold of a truth.
I say this much in justification of our confrères across the Channel and in vindication of caution and scientific logic, with which I, for one, prefer to err, rather than to be right in the company of haste and guesswork. Posterity, a somewhat short-sighted personage, who, as I have said, pays only upon results, will take no note of the protest, and will not only award to our Columbus all the credit which he deserves for being substantially in the right, but will probably abuse those of his contemporaries who were equally in the right for disbelieving him.
The death of M. A. Morlot, which took place at Berne, in February last, was announced at the last Anniversary. I borrow the substance of the following notice of his life from the "Materiaux" of M. G. de Mortillet.
M. Morlot commenced his career as a geologist, and greatly occupied himself with geology, in Austria. In Switzerland, where he subsequently took up his abode, he very successfully combined archeology with geology, and when he died was Conservator of the Archæological Museum of Berne. Although a Professor of Geology in Lausanne, he devoted himself to prehistoric studies, and greatly contributed to their progress by his investigations, his writings, and the public lectures which he was continually giving in one place or another.
The chief palæo-ethnological work of M. Morlot is entitled 'Etudes Géologico-Archéologiques en Danemark et en Suisse,' which was published at Lausanne in March 1860 in the 'Bulletin de la Société Vaudoise des Sciences Naturelles.' It is an excellent résumé, which has been of great use in spreading far and wide a knowledge of the important discoveries made in Denmark and Switzerland.
 The discovery upon which M. Morlot laid most weight, is that of the "Cône de la Tinière," which he converted into a chronometer for measuring the duration of the different prehistoric epochs. M. Morlot's last production is a great work upon Meclilembourg.
James David Forbes, late Principal of the University of St. Andrews, in Scotland, was born in Edinburgh on the 28th of April, 1809. His mother died shortly after his birth, of consumption; and the boy's delicacy was such, that his father, Mr. William Forbes, of Pitsligo, thought it well to discourage rather than to stimulate his love for knowledge, mathematical studies being especially forbidden.
But nature was stronger than paternal solicitude; and natural genius made such good use of all available opportunities for study that in 1833, at the early age of 24, Mr. Forbes was appointed Professor of Natural Philosophy in the University of Edinburgh, an office the duties of which he performed with great distinction for twenty-six years, though in the latter part of that period impeded by failing health. In 1859 Professor Forbes was appointed Principal of the United Colleges of St. Salvador and St. Leonard in the University of St. Andrews, and held these offices until his lamented death on the 31st of December, 1868.
Principal Forbes attained high distinction as an original investigator in several branches of physics, while, to the general public, he was widely known and deservedly famed as the writer who had brought the grand and profoundly interesting aspects of the Alpine world before their minds with a power and distinctness which no one since the days of Saussure had approached, when the 'Travels in the Alps' were published.
My friend and colleague Mr. Geikie, F.R.S., has given so admirable an account of Principal Forbes's relation to geological science, that I venture to reproduce what he has said on this occasion:
Principal Forbes was born in Edinburgh just twelve years after the death of the great Hutton, only seven years after the publication of the 'Illustrations of the Huttonian Theory;' and he was already a boy of ten when Mayfair died. Many of his friends had been personally acquainted with these philosophers; and the memory of the fierce Plutonian and Neptunian war was still fresh in their minds when he began to give himself to scientific pursuits. These early influences are traceable all through his life. He was profoundly impressed with the originality and truth of the views propounded by Hutton and illustrated by Playfair. He speaks with enthusiasm of the "precious lessons" which one of his friends had drawn from  the lips of Playfair and of Hall. I shall never cease to remember with gratitude that it was he who introduced me when a boy to the writings of these masters. He used to speak of Playfair's 'Illustrations of the Huttonian Theory' as one of the best books ever written upon the first principles of geological science.
Principal Forbes studied geology under Jameson, from whom he acquired a love for the mineralogical side of the science, and retained it to the last. Moreover his own predominant tendency towards physics tinged even his geological studies. Hence we find him rising on the one hand, from a contemplation of the phenomena of glaciers to a philosophical investigation of the laws under which these phenomena occuron the other, from the mere observation and collection of rocks and minerals to the natural philosophy of the operations by which they were produced.
The earliest of his geological writings which I have been able to trace is in the form of a short letter to Professor Jameson, on the occurrence of a large greenstone boulder in the Pentland Hills. It is dated from Colinton House, August 3rd, 1829, when its writer was a very little over twenty years of age. It gives an account of the position of the boulder, its composition, dimensions, and specific gravity. But the chief interest it possesses lies in the broad generalization which the young observer drew from the facts he had so carefully noted. The boulder lay upon the side of a small, steep ravine; and its position there was such as to lead him to regard the induction as undeniable, "that the excavation of the valley must have taken place subsequently to the deposition of this boulder." He remarks further that this inference as to the lateness of the erosion of valleys is forced upon us by many other instances which intimate the gradual degradation of the soil. Those who have watched the progress of geological discussion in recent years will see at how early a period our departed friend had acquired clear views upon this subject, and had based them upon the results of actual observation. This early paper is further interesting, inasmuch as it serves to indicate the special field of geology into which Forbes's natural instincts turned him, and in which he was destined in later years to reap so abundant a harvest. He had often read and treasured in his memory the eloquent passages in which Playfair, following in the path of Hutton, had expounded the erosion of valleys and the universal decay and waste of the continents. He saw that the happy suggestions and sagacious inferences of these philosophers ought to be regarded in the light rather of an outline of what remained to be discovered than as the epitome of a completed philosophy. Whatever  related to the forces which work upon the surface of the earth and effect geological changes had a special charm for him. It was this tendency which led him to wander with more than a tourist's curiosity among the glaciers of Switzerland, which first suggested to him the idea of working out by accurate observation the real cause of glacier-motion, still, in his opinion, undiscovered, and which brought him back year after year to these great mountains, where he toiled with a devotion that told at last upon his physical frame. He was the first to determine by careful measurements the amount and variations of glacier-motion. Comparing that motion to the flow of a river, he propounded the theory that "a glacier is an imperfect fluid or a viscous body, which is urged down slopes of a certain inclination by the mutual pressure of its parts." The observations and journeys which led him to this deduction are detailed in his 'Travels in the Alps,' a work in which, as in the 'Voyages dans les Alpes' of De Saussure, which he took as his model, description of scenery and narrative of adventure are happily blended with scientific observation and reasoning. The vexed question of the mechanical cause of the motion of glaciers is hardly a geological problem. I would rather refer to the abundant materials collected by Forbes in this work for the elucidation of the geological functions of glaciers. The existing operations of the ice, in scoring and polishing rocks, in transporting huge blocks of stone, and in depositing vast mounds of rubbish, are illustrated by him from many an Alpine valley. Recalling the original observations of Playfair, he points out how clear is the evidence for the former wide extension of the glaciers of Switzerland. In short, his eye seems ever to have been upon the watch for every phenomenon bearing upon the mutations of the existing surface of the land.
The lessons which he had thus laboriously learned among the living ice-rivers of the Alps, bore fruit when he came again to wander among the more mountainous regions of his own country. In the year 1840 Agassiz had made the startling announcement that the British islands had once been deeply buried under a vast mantle of snow and ice, and that the traces of its seaward motion were yet fresh and clear upon the sides of many valleys among the uplands. Following up the observations of the Swiss naturalist, Buckland and Lyell had pointed out the former existence of glaciers in the Highlands and other parts of the country. When, however, we look back upon the early discussion of this subject, we are forced to admit that conclusions were often based upon very hasty and imperfect observations. In particular, glacier moraines were often recognized in  places where no geologist would now be able to find them. Much as Forbes knew of the geological effects of ice, his natural caution kept him from taking part in this discussion for a time, until he was able to produce more accurately determined data than had, in many cases at least, been available. In the year 1845 he visited the Isle of Skye; and his eye, already trained to recognize the traces of vanished glaciers in Switzerland, was at once struck by the identity of the forms assumed by the rocks at Loch Scavaig with the roches moutonnées of the Alps. Further investigation led him to obtain complete demonstration of the former presence of a group of glaciers descending from the rugged scarps of the Cuchullin Hills. He walked over mountain and glen, filling in a rough sketch map of the glacier valleys as he went along, and in December of the same year he read a narrative of his observations to the Royal Society of Edinburgh. This was the most detailed and satisfactory account which had yet been given of the proofs that the Highlands of Britain once nourished groups of glaciers.
In the year 185I Professor Forbes undertook a journey to Norway, partly to make observations of the great solar eclipse, and partly drawn by his love of physical geography, and notably of glaciers. It was his design to compare the phenomena of glaciers in Northern Europe with those already so familiar to him in Switzerland. This he has done in a masterly way. His pages contain in a clear and succinct form, the sum of all that was known at the time regarding the snow-line and the existing glaciers of Norway. I have myself gone over much of the ground he has described, and can bear witness to the accuracy of his sketches, alike of pencil and of pen. His two chapters on the physical geography of Norway have always appeared to me to be a masterpiece of careful yet rapid observation, broad generalization, and clear description.
But though the tendency of his researches in geology was mainly towards the investigation of the phenomena connected with changes in the outline of the surface, he did not neglect the study of minerals and rocks, in which he had been trained under Jameson. Previously to 1836, with the view of learning more of the history of ancient geological upheavals, he had examined "the trap rocks of our own island, the ophites of the Pyrenees, and the serpentines of Anglesea and the Lizardthe porphyries of Northern Italythe granite veins of Mount's Bay and Glen Tiltthe ancient volcanoes of Auvergne, the Eifel, the Siebengebirge, and of Romeand the modern volcano of Vesuvius." In December 1835 he gave to the Royal Society of Edinburgh a narrative of his researches in central France, dwelling  more especially on the analogies between the volcanic rocks of that district and the trappean masses of his own country. Throughout his narratives of foreign travel, also, we everywhere meet with indications that, though busied with what had become his own more special branch of the science, he remained no indifferent observer of the rocks among which his journeys led him. He retained his fondness for mineralogy to the end. When I last saw him at St. Andrews he showed me a collection of veined agates which he had accumulated in the course of years, and with which he used often to beguile a little leisure in trying to speculate upon the manner in which the concentric siliceous coatings might have been formed.
In concluding this sketch of the late Principal's geological labours, I must not forget that some of his researches, though in themselves dealing with more or less distinctively physical questions, had often important geological bearings. Such were some of his meteorological investigations, and his carefully conducted experiments upon the temperature of the earth at different depths and in different soils near Edinburgh. These experiments were, I believe, the first made in this country, with any degree of precision, to determine the rate at which the temperature of the surface is conducted downwards, and the variations due to differences in the nature of the material through which the heat is transmitted.
Sir David Brewster was born at Jedburgh in December, 178I, and had thus attained the advanced age of more than eighty-six years, when he died in February of last year. During this long life his scientific activity was incessant, and the stream of his original papers, some 300 in number, flowed on without a check.
Nor did this singular fertility by any means exhaust Sir David Brewster's energies. He wrote in the Reviews frequently and well; he edited the 'Edinburgh Encyclopedia,' and shared in editing the 'Edinburgh Philosophical Journal,' the 'Edinburgh Journal of Science,' and the 'Philosophical Magazine.' He founded the Scottish Society of Arts, and helped to found the British Association; he was Principal of St. Andrews, and afterwards of Edinburgh University; he was long Secretary of the Royal Society of Edinburgh, and he died the President of that learned body.
With all these occupations Sir David found time to invent one of the prettiest of toys, the Kaleidoscope; to write one of the most charming of popular scientific treatises, the 'Letters on Natural Magic,' and to enter into a considerable number of controversies, in which he displayed such a capacity for the outpouring of copious  wrath, that his adversaries must have found it difficult to believe that he had anything else to do but to assail them. But this marvellous energy was never directed to geological problems. Sir David was familiar with minerals, but he regarded them with the eye of a student of optics; and even his discovery of the cavities in crystals and of their contents did not cause him to diverge from his favourite line of study. Once, indeed, he plunged into cosmology; but 'More Worlds than One hardly added to the renown which he had justly obtained as an unwearied observer and accumulator of facts in optics.
Dr. Eugene Francfort, Commendatore of the Order of St. Maurice and St. Lazarus, whose sudden decease took place at Pallanza, on the 22nd September, 1868, had for some years directed the application of English capital to the working of numerous mines near the Lago Maggiore and in the Val Anzasca. He had in early life worked at chemistry and geology in the United States, and when established in Italy exhibited such enthusiasm in the pursuit of mineralogy as secured him the friendship of many scientific men of eminence in that country. His liberality, a rare virtue among collectors, will not soon be forgotten by the friends who lament his untimely end.
Dr. Henry Porter was born July 13th, 1832, at Peterborough, in which town his father practiced as a surgeon. He received his primary education at the Hereford school under the Rev. Henry Manton, and while yet a school-boy, his interest in geology having been awakened by the perusal of one of Dr. Mantell's works, he became an enthusiastic collector and student of fossils. On leaving school he spent three years in his father's surgery, and then passed to Queen's College, Birmingham, where he greatly distinguished himself, obtaining a scholarship, two gold medals, and other honours, and becoming at the end of his three years' course of study Warnford's Prize-man. On leaving Birmingham, he continued his studies in London and Paris.
Returning to his native town, Dr. Porter entered on the practice of his profession, devoting his leisure hours to the study of the geology of the district and the formation of a collection of fossils. In 1861 he became a Fellow of this Society, and in the same year published his 'Geology of Peterborough.' This unpretentious but useful little work is an attempt to give in popular language such a sketch of the geology of a limited district as may be calculated to awaken in residents an interest in our science, and, by furnishing the necessary basis of information, lead the way to further researches. In 1863 Dr. Porter contributed a paper to this Society "On the Occurrence of Large Quantities of Fossil Wood in the Oxford Clay, near Peterborough;" he likewise, at different times, communicated various memoirs on professional subjects to the Medical Society.
It must ever be a subject of regret to geologists, as it was to the last to himself, that during the latter years of his life our esteemed associate was prevented by his feeble state of health, combined with his numerous professional and other engagements, from devoting much time to scientific pursuits. His death, which took place at the early age of thirty-six, was hastened by an accident, a fall from his horse, resulting in paralysis, which terminated fatally, August 11, 1868.
Dr. Porter was an assiduous labourer for the benefit of his native town, in which the well-known excellences of his character gained for him universal respect and good-will. His brilliant and agreeable qualities were never more conspicuous than when he played the part of a host; and no one could be better qualified for the authorship of the half-playful, half-serious little work, 'Cups and their Customs,' which was written in 1863, in conjunction with another Fellow of this Society, also deceased, Mr. George E. Roberts. The results of the geological labours of Dr. Porter are not to be estimated by his published writings alone; his extensive and valuable collection was always open to investigators of the geology of the district; and all who availed themselves of this privilege will remember with sadness his modesty and zeal not less than his geniality and hospitality.
The Rev. Joseph G. Cumming, M.A., F.G.S., Vicar of St. John's, Bethnal Green, was the son of the late Joseph Nottrall Cumming, Esq., of Matlock, where he was born on the 15th February, 1812. Mr. Cumming was educated at Oakham Grammar School; and an old Oakham school-fellow has written of him:"He was the very opposite of 'a pickle.' I do not think I ever saw such a grave earnest boy, cheerful, indeed, and eminently good-natured. He was, perhaps, about 14 years old when I first knew him, and we became close companions for at least two years afterwards, when I quitted the school. I do not remember that I ever saw him with a cricket-bat or fishing-rod; but he was very fond of talking of the wonders of Derbyshire, and presented me with some fossils. He was fond of wrestling, and we frequently walked to a quiet field some half mile from the town, and tugged at each other's collars for hours on pretty equal terms."
Mr. Cumming gained exhibitions at Oakham, and proceeded to  Emmanuel College, Cambridge, where he (Senior Opt.2 1834) was ordained in 1835, and took the curacy of his uncle, the Rev. James Cumming, Professor of Chemistry at Cambridge, and Rector of North Nuneton, Norfolk. In 1838 he was appointed Classical Master of the West Riding Proprietary School, and in 1841 Vice Principal of King William's College in the Isle of Man, where he acquired an interest in the history and antiquities of the island that never deserted him, and he contributed very largely to their illustration. Mr. Cumming remained about fifteen years in the Isle of Man, and removed on his appointment to the Mastership of King Edward's Grammar School, Lichfield. In 1858 he was appointed Warden and Professor of Classical Literature and Geology in Queen's College, Birmingham. In 1862 he was presented by the Lord Chancellor to the Rectory of Mellis, Suffolk, which he exchanged in 1867 for the Vicarage of St. John's, Bethnal Green. On the 21st September, 1868, he suddenly died whilst residing in the midst of his family circle, his removal to London, and his untiring exertions among the poor of Bethnal Green, probably, materially abridged his life. He was emphatically a hard worker both as clergyman and man of science.
Mr. Cumming was married in 1836, to Agnes, youngest daughter of J. R. Peckham, Esq., who survives him with a family of four sons and two daughters. Mr. Cumming was the author of a 'History of the Isle of Man,' and of papers on "The Geology of the Isle of Man," "The Tertiaries of the Moray Firth," "The Geology of the Calf of Man," and "The Superior Limits of the Glacial Deposits in the Isle of Man," which are published in our Journal. He became a Fellow of the Geological Society in 1846.
[Remainder of address revised into Geological Reform]
"A great reform in geological speculation seems now to have become necessary." "It is quite certain that a great mistake has been made,that British popular geology at the present time is in direct opposition to the principles of Natural Philosophy"3
"A great reform in geological speculation seems now to have become necessary."
"It is quite certain that a great mistake has been made,that British popular geology at the present time is in direct opposition to the principles of Natural Philosophy"3
In reviewing the course of geological thought during the past year, for the purpose of discovering those matters to which I might most fitly direct your attention in the Address which it now becomes my duty to deliver from the Presidential Chair, the two somewhat alarming sentences which I have just read, and which occur in an  able and interesting essay, by an eminent natural Philosopher, rose into such prominence before my mind that they eclipsed everything else.
It surely is a matter of paramount importance for the British geologists (some of them very popular geologists too) here in solemn annual session assembled, to inquire whether the severe judgment thus passed upon them by so high an authority as Sir William Thomson is one to which they must plead guilty sans phrase, or whether they are prepared to say "not guilty," and appeal for a reversal of the sentence to that higher court of educated scientific opinion to which we are all amenable.
As your attorney-general for the time being, I thought I could not do better than get up the case with a view of advising you. It is true that the charges brought forward by the other side involve the consideration of matters quite foreign to the pursuits with which I am ordinarily occupied; but in that respect I am only in the position which is, nine times out of ten, occupied by counsel, who nevertheless contrive to gain their causes, mainly by force of motherwit and common sense, aided by some training in other intellectual exercises.
Nerved by such precedents, I proceed to put my pleading before you.
And the first question with which I propose to deal is, What is it to which Sir W. Thomson refers when he speaks of "geological speculation" and "British popular geology"?
I find three more or less contradictory systems of geological thought, each of which might fairly enough claim these appellations standing side by side in Britain. I shall call one of them Catastrophism, another Uniformitarianism, the third Evolutionism; and I shall try briefly to sketch the characters of each, that you may say whether the classification is or is not exhaustive.
By Catastrophism I mean any form of geological speculation which, in order to account for the phenomena of geology, supposes the operation of forces different in their nature, or immeasurably different in power, from those which we at present see in action in the universe.
The Mosaic cosmogony is, in this sense, catastrophic, because it assumes the operation of extra-natural power. The doctrine of violent upheavals, débâcles, and cataclysms in general is catastrophic, so far as it assumes that these were brought about by causes which have now no parallel. There was a time when catastrophism might pre-eminently have claimed the title of "British popular geology;" and assuredly it has yet many adherents, and reckons among its supporters some of the most honoured members of this Society.
By Uniformitarianism I mean pre-eminently the teaching of Hutton and of Lyell.
That great, though incomplete work, 'The Theory of the Earth,' seems to me to be one of the most remarkable contributions to geology which is recorded in the annals of the science. So far as the non-living world is concerned, uniformitarianism lies there, not only in germ, but in blossom and fruit.
If one asks how it is that Hutton was led to entertain views so far in advance of those prevalent in his time in some respects, while in others they seem almost curiously limited, the answer appears to me to be plain.
Hutton was in advance of the geological speculation of his time, because, in the first place, he had amassed a vast store of knowledge of the facts of geology, gathered by personal observation in travels of considerable extent, and because, in the second place, he was thoroughly trained in the physical and chemical science of his day, and thus possessed, as much as any one in his time could possess it, the knowledge which was requisite for the just interpretation of geological phenomena, and the habit of thought which fits a man for scientific inquiry.
It is to this thorough scientific training that I ascribe Hutton's steady and persistent refusal to look to other causes than those now in operation for the explanation of geological phenomena.
Thus he writes:"I do not pretend, as he [M. de Luc] does in his theory, to describe the beginning of things. I take things such as I find them at present; and from these I reason with regard to that which must have been."4
And again:"A theory of the earth, which has for object truth, can have no retrospect to that which had preceded the present order of the world; for this order alone is what we have to reason upon; and to reason without data is nothing but delusion. A theory, therefore, which is limited to the actual constitution of this earth cannot be allowed to proceed one step beyond the present order of things."5
And so clear is he that no causes besides such as are now in operation are needed to account for the character and disposition of the components of the crust of the earth, that he says, broadly and boldly:"....There is no part of the earth which has not had the same origin, so far as this consists in that earth being collected  at the bottom of the sea, and afterwards produced, as land, along with masses of melted substances, by the operation of mineral causes."6
But other influences were at work upon Hutton beside those of a mind logical by nature, and scientific by sound training; and the peculiar turn which his speculations took seems to me to be unintelligible unless these be taken into account. The arguments of the French astronomers and mathematicians, which, at the end of the last century, were held to demonstrate the existence of a compensating arrangement among the celestial bodies, whereby all perturbations eventually reduced themselves to oscillations on each side of a mean position, and the stability of the solar system was secured, had evidently taken strong hold of Hutton's mind.
In those oddly constructed periods which seem to have prejudiced many persons against reading his works, but which are full of that peculiar, if unattractive, eloquence which flows from mastery of the subject, Hutton says:
"We have now got to the end of our reasoning; we have no data further to conclude immediately from that which actually is. But we have got enough; we have the satisfaction to find, that in nature there is wisdom, system, and consistency. For having, in the natural history of this earth, seen a succession of worlds, we may from this conclude that there is a system in nature; in like manner as from seeing revolutions of the planets, it is concluded that there is a system by which they are intended to continue those revolutions. But if the succession of worlds is established in the system of nature, it is in vain to look for anything higher in the origin of the earth. The result, therefore, of this physical inquiry is, that we find no vestige of a beginning,no prospect of an end."7
Yet another influence worked strongly upon Hutton. Like most philosophers of his age, he coquetted with those final causes which have been named barren virgins, but which might be more fitly termed the hetairæ of philosophy, so constantly have they led men astray. The final cause of the existence of the world is, for Hutton, the production of life and intelligence.
"We have now considered the globe of this earth as a machine constructed upon chemical as well as mechanical principles, by which its different parts are all adapted, in form, in quality, and in quantity, to a certain end; an end attained with certainty or success; and an end from which we may perceive wisdom, in contemplating the means employed. 
"But is this world to be considered thus merely as a machine, to last no longer than its parts retain their present position, their proper forms and qualities? Or may it not be also considered as an organized body? such as has a constitution in which the necessary decay of the machine is naturally repaired, in the exertion of those productive powers by which it had been formed.
"This is the view in which we are now to examine the globe; to see if there be, in the constitution of this world, a reproductive operation, by which a ruined constitution may be again repaired, and a duration or stability thus procured to the machine, considered as a world sustaining plants and animals."8
Kirwan and the other Philistines of the day accused Hutton of declaring that his theory implied that the world never had a beginning, and never differed in condition from its present state. Nothing could be more grossly unjust, as he expressly guards himself against any such conclusion in the following terms:
"But in thus tracing back the natural operations which have succeeded each other, and mark to us the course of time past, we come to a period in which we cannot see any farther. This, however, is not the beginning of the operations which proceed in time and according to the wise economy of this world; nor is it the establishing of that which, in the course of time, had no beginning; it is only the limit of our retrospective view of those operations which have come to pass in time, and have been conducted by supreme intelligence."9
I have spoken of Uniformitarianism as the doctrine of Hutton and of Lyell. If I have quoted the older writer rather than the newer, it is because his works are little known, and his claims on our veneration too frequently forgotten, not because I desire to dim the fame of his eminent successor. Few of the present generation of geologists have read Playfair's 'Illustrations,' fewer still the original 'Theory of the Earth;' the more is the pity; but which of us has not thumbed every page of the 'Principles of Geology'? I think that he who writes fairly the history of his own progress in geological thought will not be able to separate his debt to Hutton from his obligations to Lyell; and the history of the progress of individual geologists is the history of geology.
No one can doubt that the influence of uniformitarian views has been enormous, and, in the main, most beneficial and favourable to the progress of sound geology.
Nor can it be questioned that uniformitarianism has even a stronger  title than catastrophism to call itself the geological speculation of Britain, or, if you will, British popular geology. For it is eminently a British doctrine, and has even now made comparatively little progress on the continent of Europe. Nevertheless it seems to me to be open to serious criticism upon one of its aspects.
I have shown how unjust was the insinuation that Hutton denied a beginning to the world. But it would not be unjust to say that he persistently, in practice, shut his eyes to the existence of that prior and different state of things which in theory he admitted; and in this aversion to look beyond the veil of stratified rocks Lyell follows him.
Hutton and Lyell alike agree in their indisposition to carry their speculations a step beyond the period recorded in the most ancient strata now open to observation in the crust of the earth. This is, for Hutton, "the point in which we cannot see any farther;" while Lyell tells us,
"The astronomer may find good reasons for ascribing the earth's form to the original fluidity of the mass in times long antecedent to the first introduction of living beings into the planet; but the geologist must be content to regard the earliest monuments which it is his task to interpret, as belonging to a period when the crust had already acquired great solidity and thickness, probably as great as it now possesses, and when volcanic rocks, not essentially differing from those now produced, were formed from time to time, the intensity of volcanic heat being neither greater nor less than it is now."10
And again, "As geologists, we learn that it is not only the present condition of the globe which has been suited to the accommodation of myriads of living creatures, but that many former states also have been adapted to the organization and habits of prior races of beings. The disposition of the seas, continents and islands, and the climates have varied; the species likewise have been changed; and yet they have all been so modelled, on types analogous to those of existing plants and animals, as to indicate, throughout, a perfect harmony of design and unity of purpose. To assume that the evidence of the beginning, or end, of so vast a scheme lies within the reach of our philosophical inquiries, or even of our speculations, appears to be inconsistent with a just estimate of the relations which subsist between the finite powers of man and the attributes of an infinite and eternal being.11
The limitations implied in these passages appear to me to constitute the weakness and the logical defect of uniformitarianism. No  one will impute blame to Hutton that, in face of the imperfect condition, in his day, of those physical sciences which furnish the keys to the riddles of geology, he should have thought it practical wisdom to limit his theory to an attempt to account for "the present order of things"; but I am at a loss to comprehend why, for all time, the geologist must be content to regard the oldest fossiliferous rocks as the ultima Thule of his science, or what there is inconsistent with the relations between the finite and the infinite mind in the assumption that we may discern somewhat of the beginning, or of the end, of this speck in space we call our earth. The finite mind is certainly competent to trace out the development of the fowl within the egg; and I know not on what ground it should find more difficulty in unravelling the complexities of the development of the earth. In fact, as Kant has well remarked,12 the cosmical process is really simpler than the biological.
This attempt to limit at a particular point the progress of inductive and deductive reasoning from the things which are to those which werethis faithlessness to its own logic, seems to me to have cost Uniformitarianism the place, as the permanent form of geological speculation, which it might otherwise have held.
It remains that I should place before you what I understand to be the third phase of geological speculationnamely Evolutionism.
I shall not make what I have to say on this head clear unless I diverge, or seem to diverge, for a while from the direct path of my discourse, so far as to explain what I take to be the scope of geology itself. I conceive geology to be the history of the earth in precisely the same sense as biology is the history of living beings; and I trust you will not think that I am overpowered by the influence of a dominant pursuit if I say that I trace a close analogy between these two histories.
If I study a living being, under what heads does the knowledge I obtain fall? I can learn its structure, or what we call its Anatomy; and its Development, or the series of changes which it passes through to acquire its complete structure. Then I find that the living being has certain powers resulting from its own activities, and the interaction of these with the activities of other thingsthe knowledge of which is Physiology. Beyond this the living being  has a position in space and time, which is its Distribution. All these form the body of ascertainable facts which constitute the status quo of the living creature. But these facts have their causes; and the ascertainment of these causes is the doctrine of Ætiology.
If we consider what is knowable about the earth, we shall find that such earth-knowledgeif I may so translate the word geologyfalls into the same categories.
What is termed stratigraphical geology is neither more nor less than the anatomy of the earth; and the history of the succession of the formations is the history of a succession of such anatomies, or corresponds with development, as distinct from generation.
The internal heat of the earth, the elevation and depression of its crust, its belchings forth of vapours, ashes, and lava are its activities in as strict a sense as are warmth and the movements and products of respiration the activities of an animal. The phenomena of the seasons, of the trade winds, of the Gulf-stream are as much the results of the reaction between these inner activities anti outward forces, as are the budding of the leaves in spring and their falling in autumn the effects of the interaction between the organization of a plant and the solar light and heat. And as the study of the activities of the living being is called its physiology, so are these phenomena the subject-matter of an analogous telluric physiology, to which we sometimes give the name of meteorology, sometimes that of physical geography, sometimes that of geology. Again, the earth has a place in space and in time, and relations to other bodies in both these respects, which constitute its distribution. This subject is usually left to the astronomer; but a knowledge of its broad outlines seems to me to be an essential constituent of the stock of geological ideas.
All that can be ascertained concerning the structure, succession of conditions, actions, and position in space, of the earth is the matter of fact of its natural history. But, as in biology, there remains the matter of reasoning from these facts to their causes, which is just as much science as the other, and indeed more; and this constitutes geological Ætiology.
Having regard to this general scheme of geological knowledge and thought, it is obvious that geological speculation may be, so to speak, anatomical and developmental speculation, so far as it relates to points of stratigraphical arrangement which are out of reach of direct observation; or it may be physiological speculation, so far as it relates to undetermined problems relative to the activities of the earth; or it may be distributional speculation, if it deals with modifications of the earth's place in space; or, finally, it will be Biological speculation, if it attempts to deduce the history of the world, as a whole, from the known properties of the matter of the earth in the conditions in which the earth has been placed.
For the purposes of the present discourse I may take this last to be what is meant by 'geological speculation.'
Now uniformitarianism, as we have seen, tends to ignore geological speculation in this sense altogether. The one point the catastrophists and the uniformitarians agreed upon when this Society was founded, was to ignore it. And you will find, if you look back into our records, that our revered fathers in geology plumed themselves a good deal upon the practical sense and wisdom of this proceeding. As a temporary measure, I do not presume to challenge its wisdom; but in all organized bodies temporary changes are apt to produce permanent effects; and as time has slipped by, altering all the conditions which may have made such mortification of the scientific flesh desirable, I think the effect of the stream of cold water which has steadily flowed over geological speculation within these walls, has been of doubtful beneficence.
The sort of geological speculation to which I am now referring (geological ætiology, in short) was created as a science by that famous philosopher Immanuel Kant, when, in 1755, he wrote his 'General Natural History and Theory of the Celestial Bodies; or an attempt to account for the constitution and the mechanical origin of the universe upon Newtonian principles.'13
In this very remarkable, but seemingly little-known treatise,14 Kant expounds a complete cosmogony, in the shape of a theory of the causes which have led to the development of the universe from diffused atoms of matter endowed with simple attractive and repulsive forces.
"Give me matter," says Kant, "and I will build the world;" and he proceeds to deduce from the simple data from which he starts, a doctrine in all essential respects similar to the well-known "Nebular Hypothesis" of Laplace.15 He accounts for the relation of the masses and the densities of the planets to their distances from the sun, for the eccentricities of their orbits, for their rotations, for their  satellites, for the general agreement in the direction of rotation among the celestial bodies, for Saturn's ring, and for the zodiacal light. He finds in each system of worlds indications that the attractive force of the central mass will eventually destroy its organization by concentrating upon itself the matter of the whole system; but, as the result of this concentration, he argues for the development of an amount of heat which will dissipate the mass once more into a molecular chaos such as that in which it began.
Kant pictures to himself the universe as once an infinite expansion of formless and diffused matter. At one point of this he supposes a single centre of attraction set up, and by strict deductions from admitted dynamical principles shows how this must result in the development of a prodigious central body surrounded by systems of solar and planetary worlds in all stages of development. In vivid language he depicts the great world-maelstrom widening the margins of its prodigious eddy in the slow progress of millions of ages, gradually reclaiming more and more of the molecular waste, and converting chaos into cosmos. But what is gained at the margin is lost in the centre; the attractions of the central systems bring their constituents together, which then by the heat evolved are converted once more into molecular chaos. Thus the worlds that are, lie between the ruins of the worlds that have been and the chaotic materials of the worlds that shall be; and in spite of all waste and destruction Cosmos is extending his borders at the expense of Chaos.
Kant's further application of his views to the earth itself is to be found in his 'Treatise on Physical Geography'16 (a term under which the then unknown science of geology was included), a subject which he had studied with very great care and on which he lectured for many years. The fourth section of the first part of this Treatise is called "History of the great changes which the earth has formerly undergone and is still undergoing," and is in fact a brief and pregnant essay upon the principles of geology. Kant gives an account first "of the gradual changes which are now taking place" under the heads of such as are caused by earthquakes, such as are brought about by rain and rivers, such as are effected by the sea, such as are produced by winds and frost, and, finally, such as result from the operations of man.
The second part is devoted to the "Memorials of the changes which the earth has undergone in remote antiquity." These are enumerated as:A. Proofs that the sea formerly covered the whole earth. B. Proofs that the sea has often been changed into dry land and  then again into sea. C. A discussion of the various theories of the earth put forward by Scheuchzer, Moro, Bonnet, Woodward, White, Leibnitz, Linnæus, and Buffon.
The third part contains an "Attempt to give a sound explanation of the ancient history of the earth."
I suppose that it would be very easy to pick holes in the details of Kant's speculations, whether cosmological or specially telluric in their application. But, for all that, he seems to me to have been the first person to frame a complete system of geological speculation by founding the doctrine of evolution.
With as much truth as Hutton, Kant could say, "I take things just as I find them at present, and from these I reason with regard to that which must have been." Like Hutton, he is never tired of pointing out that "in nature there is wisdom, system, and constancy." And as in these great principles, so in believing that the cosmos has a reproductive operation "by which a ruined constitution may be repaired" he forestalls Hutton; while, on the other hand, Kant is true to science. He knows no bounds to geological speculation but those of the intellect. He reasons back to a beginning of the present state of things; he admits the possibility of an end.
I have said that the three schools of geological speculation which I have termed Catastrophism, Uniformitarianism, and Evolutionism are commonly supposed to be antagonistic to one another; and I presume it will have become obvious that, in my belief, the last is destined to swallow up the other two. But it is proper to remark that each of the latter has kept alive the tradition of precious truths.
Catastrophism has insisted upon the existence of a practically unlimited bank of force, on which the theorist might draw; and it has cherished the idea of the development of the earth from a state in which its form, and the forces which it exerted, were very different from those we now know. That such difference of form and power once existed is a necessary part of the doctrine of evolution.
Uniformitarianism, on the other hand, has with equal justice insisted upon a practically unlimited bank of time, ready to discount any quantity of hypothetical paper. It has kept before our eyes the power of the infinitely little, time being granted, and has compelled us to exhaust known causes before flying to the unknown.
To my mind there appears to be no sort of necessary theoretical antagonism between Catastrophism and Uniformitarianism. On the contrary, it is very conceivable that catastrophes may be part and parcel of uniformity. Let me illustrate my case by analogy. The  working of a clock is a model of uniform action; good time-keeping means uniformity of action. But the striking of the clock is essentially a catastrophe; the hammer might be made to blow up a barrel of gunpowder, or turn on a deluge of water; and, by proper arrangement, the clock, instead of marking the hours, might strike at all sorts of irregular intervals, never twice alike in the intervals, force, or number of its blows. Nevertheless all these irregular and apparently lawless catastrophes would be the result of an absolutely uniformitarian action; and we might have two schools of clock-theorists, one studying the hammer and the other the pendulum.
Still less is there any necessary antagonism between either of these doctrines and that of Evolution, which embraces all that is sound in both Catastrophism and Uniformitarianism, while it rejects the arbitrary assumptions of the one and the, as arbitrary, limitations of the other. Nor is the value of the doctrine of Evolution to the philosophic thinker diminished by the fact that it applies the same method to the living and the not-living world, and embraces in one stupendous analogy the growth of a solar system from molecular chaos, the shaping of the earth from the nebulous cubhood of its youth, through innumerable changes and immeasurable ages, to its present form, and the development of a living being from the shapeless mass of protoplasm we term a germ.
I do not know whether Evolutionism can claim that amount of currency which would entitle it to be called British popular geology; but, more or less vaguely, it is assuredly present in the minds of most geologists.
Such being the three phases of geological speculation, we are now in a position to inquire which of these it is that Sir William Thomson calls upon us to reform in the passages which I have cited.
It is obviously Uniformitarianism which the distinguished physicist takes to be the representative of geological speculation in general. And thus a first issue is raised, inasmuch as many persons (and those not the least thoughtful among the younger geologists) do not accept strict Uniformitarianism as the final form of geological speculation. We should say, if Hutton and Playfair declare the course of the world to have been always the same, point out the fallacy by all means, but in so doing do not imagine that you are proving modern geology to be in opposition to natural philosophy. I do not suppose that, at the present day, any geologist would be found to maintain absolute Uniformitarianism, to deny that the rapidity of the rotation of the earth may be diminishing, that the sun may be waxing dim,  or that the earth itself may be cooling. Most of us, I suspect, are Gallios, "who care for none of these things," being of opinion that, true or fictitious, they have made no practical difference to the earth, during the period of which a record is preserved in stratified deposits.
The accusation that we have been running counter to the principles of natural philosophy, therefore, is devoid of foundation. The only question which can arise is whether we have, or have not, been tacitly making assumptions which are in opposition to certain conclusions which may be drawn from those principles. And this question subdivides itself into two:the first, are we really contravening such conclusions? the second, if we are, are those conclusions so firmly based that we may not contravene them? I reply in the negative to both these questions, and I will give you my reasons for so doing. Sir William Thomson believes that he is able to prove by physical reasonings, "that the existing state of things on the earth, life on the earthall geological history showing continuity of lifemust be limited within some such period of time as one hundred million years" (loc. cit., p. 25).
The first inquiry which arises plainly is, has it ever been denied that this period may be enough for the purposes of geology?
The discussion of this question is greatly embarrassed by the vagueness with which the assumed limit is, I will not say defined, but indicated,"some such period of past time as one hundred million years." Now does this mean that it may have been two, or three, or four hundred million years? because this really makes all the differences.17
I presume that 100,000 feet may be taken as a full allowance for the total thickness of stratified rocks containing traces of life; 100,000 divided by 100,000,000=0.001. Consequently, the deposit of 100,000 feet of stratified rock in 100,000,000 years means that the deposit has taken place at the rate of 1/1000 of a foot, or, say, 1/83 of an inch, per annum.
Well, I do not know that any one is prepared to maintain that, even making all needful allowances, the stratified rocks may not have been formed, on the average, at the rate of 1/25 of an inch per annum. I suppose that if such could be shown to be the limit of world-growth, we could put up with the allowance without feeling that our speculations had undergone any revolution. And perhaps,  after all, the qualifying phrase "some such period" may not necessitate the assumption of more than 1/166, or 1/249, or 1/332 of an inch of deposit, per year, which, of course, would give us still more ease and comfort.
But it may be said that it is biology, and not geology, which asks for so much timethat the succession of life demands vast intervals; but this appears to me to be reasoning in a circle. Biology takes her time from geology. The only reason we have for believing in the slow rate of the change in living forms is the fact that they persist through a series of deposits which geology informs us have taken a long while to make. If the geological clock is wrong, all the naturalist will have to do is to modify his notions of the rapidity of change accordingly. And I venture to point out that, when we are told that the limitation of the period during which living beings have inhabited this planet to one, two, or three hundred million years requires a complete revolution in geological speculation, the onus probandi rests on the maker of the assertion, who brings forward not a shadow of evidence in its support.
Thus, if we accept the limitation of time placed before us by Sir W. Thomson, it is not obvious, on the face of the matter, that we shall have to alter, or reform, our ways in any appreciable degree; and we may therefore proceed with much calmness, and indeed, much indifference to the result, to inquire whether that limitation is justified by the arguments employed in its support.
These arguments are three in number:
I. The first is based upon the undoubted fact that the tides tend to retard the rate of the earth's rotation upon its axis. That this must be so is obvious, if one considers roughly that the tides result from the pull which the sun and the moon exert upon the sea, causing it to act as a sort of break upon the rotating solid earth.
Kant, who was by no means a mere "abstract philosopher," but a good mathematician and well versed in the physical science of his time, not only proved this in an essay of exquisite clearness and intelligibility, now more than a century old,18 but deduced from it some of its more important consequences, such as the constant turning of one face of the moon towards the earth.
But there is a long step from the demonstration of a tendency to the estimation of the practical value of that tendency, which is all  with which we are at present concerned. The facts bearing on this point appear to stand as follows:
It is a matter of observation that the moon's mean motion is (and has for the last 3000 years been) undergoing an acceleration relatively to the rotation of the earth. Of course this may result from one of two causes: the moon may really have been moving more swiftly in its orbit; or the earth may have been rotating more slowly on its axis.
Laplace believed he had accounted for this phenomenon by the fact that the eccentricity of the earth's orbit has been diminishing throughout these 3000 years. This would produce a diminution of the mean attraction of the sun on the moon, or, in other words, an increase in the attraction of the earth on the moon, and, consequently, an increase in the rapidity of the orbital motion of the latter body. Laplace, therefore, laid the responsibility of the acceleration upon the moon; and if his views were correct, the tidal retardation must either be insignificant in amount, or be counteracted by some other agency.
Our great astronomer Adams, however, appears to have found a flaw in Laplace's calculation, and to have shown that only half the observed retardation could be accounted for in the way he had suggested. There remains, therefore, the other half to be accounted for; and here, in the absence of all positive knowledge, three sets of hypotheses have been suggested:
a.. M. Delaunay suggests that the earth is at fault, in consequence of the tidal retardation. Messrs. Adams, Thomson, and Tait work out this suggestion, and, "on a certain assumption as to the proportion of retardations due to the sun and the moon," find the earth may lose 22 seconds of time in a century from this cause. (Sir W. Thomson, L. c., p. 14.)
b. But M. Dufour suggests that the retardation of the earth (which is hypothetically assumed to exist) may be due in part, or wholly, to the increase of the moment of inertia of the earth by meteors falling upon its surface. This suggestion also meets with the entire approval of Sir W. Thomson, who shows that meteor-dust, accumulating at the rate of 1 foot in 4000 years, would account for the remainder of retardation. (L. c., p. 27.)
c. Thirdly, Sir W. Thomson brings forward an hypothesis of his own with respect to the cause of the hypothetical retardation of the earth's rotation:
"Let us suppose ice to melt from the polar regions (20° round each pole, we may say) to the extent of something more than a foot  thick, enough to give 1.1 foot of water over those areas, or 0.006 of a foot of water if spread over the whole globe, which would in reality raise the sea-level by only some such undiscoverable difference as 3/4 of an inch or an inch. This or the reverse, which we believe might happen any year, and could certainly not be detected without far more accurate observations and calculations for the mean sea-level than any hitherto made, would slacken or quicken the earth's rate as a time-keeper by one-tenth of a second per year." (L. c., p. 27)
I do not presume to throw the slightest doubt upon the accuracy of any of the calculations made by such distinguished mathematicians as those who have made the suggestions I have cited. On the contrary, it is necessary to my argument to assume that they are all correct. But I desire to point out that this seems to be one of the many cases in which the admitted accuracy of mathematical processes is allowed to throw a wholly inadmissible appearance of authority over the results obtained by them. Mathematics may be compared to a mill of exquisite workmanship, which grinds you stuff of any degree of fineness; but, nevertheless, what you get out depends on what you put in; and as the grandest mill in the world will not extract wheat-flour from peascods, so pages of formulæ will not get a definite result out of loose data.
In the present instance it appears to be admitted:
I. That it is not absolutely certain, after all, whether the moon's mean motion is undergoing acceleration, or the earth's rotation retardation.19 And yet this is the key of the whole position.
2. If the rapidity of the earth's rotation is diminishing, it is not certain how much of that retardation is due to tidal friction,how much to meteors,how much to possible excess of melting over accumulation of polar ice during the period covered by observation, which amounts, at the outside, to not more than 2600 years.
3. The effect of a different distribution of land and water in modifying the retardation caused by tidal friction, and of reducing it, under some circumstances, to a minimum, does not appear to be taken into account.
4. During the Miocene epoch the polar ice was certainly many feet thinner than it has been during or since the Glacial epoch. Sir W. Thomson tells us that the accumulation of something more than a foot of ice around the poles (which implies the withdrawal of, say, an inch of water from the general surface of the sea) will cause the earth to rotate quicker by one-tenth of a second per annum. It would  appear, therefore, that the earth may have been rotating, throughout the whole period which has elapsed from the commencement of the Glacial epoch down to the present time, one, or more, seconds per annum quicker than it rotated during the Miocene epoch.
But, according to Sir W. Thomson's calculation, tidal retardation will only account for a retardation of 22" in a century, or 22/100 (say 1/5) of a second per annum.
Thus, assuming that the accumulation of polar ice since the Miocene epoch has only been sufficient to produce ten times the effect of a coat of ice one foot thick, we shall have an accelerating cause which covers all the loss from tidal action, and leaves a balance of 4/5 of a second per annum in the way of acceleration.
If tidal retardation can be thus checked and overthrown by other temporary conditions, what becomes of the confident assertion, based upon the assumed uniformity of tidal retardation, that ten thousand million years ago the earth must have been rotating more than twice as fast as at present, and, therefore, that we geologists are "in direct opposition to the principles of Natural Philosophy" if we spread geological history over that time?
II. The second argument is thus stated by Sir W. Thomson:"An article, by myself, published in 'Macmillan's Magazine' for March 1862, on the age of the sun's heat, explains results of investigation into various questions as to possibilities regarding the amount of heat that the sun could have, dealing with it as you would with a stone, or a piece of matter, only taking into account the sun's dimensions, which showed it to be possible that the sun may have already illuminated the earth for as many as one hundred million years, but at the same time rendered it almost certain that he had not illuminated the earth for five hundred millions of years. The estimates here are necessarily very vague; but yet, vague as they are, I do not know that it is possible, upon any reasonable estimate founded on known properties of matter, to say that we can believe the sun has really illuminated the earth for five hundred million years." (L. c., p. 20.)
I do not wish to "Hansardize" Sir William Thomson by laying much stress on the fact that, only fifteen years ago, he entertained a totally different view of the origin of the sun's heat, and believed that the energy radiated from year to year was supplied from year to yeara doctrine which would have suited Hutton perfectly. But the fact that so eminent a physical philosopher has thus recently held views opposite to those which he now entertains, and that he confesses his own estimates to be "very vague," justly entitles us to disregard those estimates if any distinct facts on our side go against them.  However, I am not aware that such facts exist. As I have already said, for anything that I know, one, two, or three hundred millions of years may serve the needs of geologists perfectly well.
III. The third line of argument is based upon the temperature of the interior of the earth. Sir W. Thomson refers to certain investigations which prove that the present thermal condition of the interior of the earth implies either a heating of the earth within the last 20,000 years of as much as 100° F., or a greater heating all over the surface at some time further back than 20,000 years, and then proceeds thus:
"Now, are geologists prepared to admit that, at some time within the last 20,000 years, there has been all over the earth so high a temperature as that? I presume not; no geologistno modern geologistwould for a moment admit the hypothesis that the present state of underground heat is due to a heating of the surface at so late a period as 20,000 years ago. If that is not admitted, we are driven to a greater heat at some time more than 20,000 years ago. A greater heating all over the surface than 100° Fahrenheit would kill nearly all existing plants and animals, I may safely say. Are modern geologists prepared to say that all life was killed off the earth 50,.000, 100.000, or 200,000 years ago? For the uniformity theory, the further back the time of high surface-temperature is put the better; but the further back the time of heating, the hotter it must have been. The best for those who draw most largely on time is that which puts it furthest back; and that is the theory that the heating was enough to melt the whole. But even if it was enough to melt the whole, we must still admit some limit, such as fifty million years, one hundred million years, or two or three hundred million years ago. Beyond that we cannot go." (L. c., p. 24.)
It will be observed that the "limit" is once again of the vaguest, ranging from 50,000,000 years to 300,000,000. And the reply is, once more, that, for anything that can be proved to the contrary, one or two hundred million years might serve the purpose, even of a thoroughgoing Huttonian uniformitarian, very well.
But if, on the other hand, the 100,000,000 or 200,000,000 years appear to be insufficient for geological purposes, we must closely criticise the method by which the limit is reached. The argument is simple enough. Assuming the earth to be nothing but a cooling mass, the quantity of heat lost per year, supposing the rate of cooling to have been uniform, multiplied by any given number of years, will give the minimum temperature that number of years ago.
But is the earth nothing but a cooling mass, "like a hot-water jar  such as is used in carriages," or "a globe of sandstone"? and has its cooling been uniform? An affirmative answer to both these questions seems to be necessary to the validity of the calculations on which Sir W. Thomson lays so much stress.
Nevertheless it surely may be urged that such affirmative answers are purely hypothetical, and that other suppositions have an equal right to consideration.
For example, is it not possible that, at the prodigious temperature which would seem to exist at 100 miles below the surface, all the metallic bases may behave as mercury does at a red heat, when it refuses to combine with oxygen; while, nearer the surface, and therefore at a lower temperature, they may enter into combination (as mercury does with oxygen a few degrees below its boiling-point) and so give rise to a heat which is totally distinct from that which they possess as cooling bodies? And has it not also been proved by recent researches that the quality of the atmosphere may immensely affect its permeability to heat, and consequently profoundly modify the rate of cooling of the globe as a whole?
I do not think it can be denied that such conditions may exist, and may so greatly affect the supply and the loss of terrestrial heat as to destroy the value of any calculations which leave them out of sight.
My functions as your advocate are at an end. I speak with more than the sincerity of a mere advocate when I express the belief that the case against us has entirely broken down. The cry for reform which has been raised without is superfluous, inasmuch as we have long been reforming from within with all needful speed. And the critical examination of the grounds upon which the very grave charge of opposition to the principles of Natural Philosophy has been brought against us rather shows that we have exercised a wise discrimination in declining to meddle with our foundations at the bidding of the first passer-by who fancies our house is not so well built as it might be.
1 See Lyell, 'Antiquity o f Man,' p. 214-217. 2 See Cambridge Calendar. 3 On Geological Time. By Sir W. Thomson, LL D Transactions of the Geological Society of Glasgow, vol. iii. 4 'The Theory of the Earth," vol. i, p. 173, note 5 Ib. p. 281. 6 'The Theory of the Earth,' p. 371. 7 Ib. p. 200. 8 'The Theory of the Earth,' pp. 16, 17. 9 Ib. p. 223. 10 Principles of Geology, vol. ii, p. 211. 11 Ib. p. 613. 12 "Man darf es sich also nicht befremden lassen, wenn ich mich unterstehe zu sagen, dass eher die Bildung aller Himmelskörper, die Ursache ihrer Bewegungen, kurz der Ursprung der ganzen gegenwartigen Verfassung des Weltbaues werden können eingesehen werden, ehe die Erzeugung eines einzigen Krauts oder einer Raupe aus mechanischen Gründen, deutlich und vollstandig kund werden wird."Kant's 'Sämmtliche Werke,' Bd. I. p. 220. 13 Grant (' History of Physical Astronomy,' p. 574) makes but the briefest reference to Kant. 14 "Allgemeine Naturgeschichte und Theorie des Himmels; oder Versuch von der Verfassung und dem mechanischen Ursprunge des ganzen Weltgebaudes nach Newton'schen Grundsatzen abgehandelt."Kant's 'Sämmtliche Werke,' Bd. I. p. 207. 15 'Systeme du Monele,' tom. ii. chap. 6. 16 Kant's 'Sämmtliche Werke,' Bd. VIII., p. 145. 17 Sir William Thomson implies (loc. cit., p. 16) that the precise time is of no consequence, "the principle is the same"; but as the principle is admitted, the whole discussion turns on its practical results. 18 "Untersuchung der Frage ob die Erde in ihrer Umdrehung urn die Achse, wodurch sie die Abwechselung des Tages und der Nacht hervorbringt, einige Veränderung seit den ersten Zeiten ihres Ursprunges erlitten habe, &c."Kant's 'Sämmtliche Werke,' Bd. I. p. 178. 19 It will be understood that I do not wish to deny that the earth's rotation may be undergoing retardation.
1 See Lyell, 'Antiquity o f Man,' p. 214-217.
2 See Cambridge Calendar.
3 On Geological Time. By Sir W. Thomson, LL D Transactions of the Geological Society of Glasgow, vol. iii.
4 'The Theory of the Earth," vol. i, p. 173, note
5 Ib. p. 281.
6 'The Theory of the Earth,' p. 371.
7 Ib. p. 200.
8 'The Theory of the Earth,' pp. 16, 17.
9 Ib. p. 223.
10 Principles of Geology, vol. ii, p. 211.
11 Ib. p. 613.
12 "Man darf es sich also nicht befremden lassen, wenn ich mich unterstehe zu sagen, dass eher die Bildung aller Himmelskörper, die Ursache ihrer Bewegungen, kurz der Ursprung der ganzen gegenwartigen Verfassung des Weltbaues werden können eingesehen werden, ehe die Erzeugung eines einzigen Krauts oder einer Raupe aus mechanischen Gründen, deutlich und vollstandig kund werden wird."Kant's 'Sämmtliche Werke,' Bd. I. p. 220.
13 Grant (' History of Physical Astronomy,' p. 574) makes but the briefest reference to Kant.
14 "Allgemeine Naturgeschichte und Theorie des Himmels; oder Versuch von der Verfassung und dem mechanischen Ursprunge des ganzen Weltgebaudes nach Newton'schen Grundsatzen abgehandelt."Kant's 'Sämmtliche Werke,' Bd. I. p. 207.
15 'Systeme du Monele,' tom. ii. chap. 6.
16 Kant's 'Sämmtliche Werke,' Bd. VIII., p. 145.
17 Sir William Thomson implies (loc. cit., p. 16) that the precise time is of no consequence, "the principle is the same"; but as the principle is admitted, the whole discussion turns on its practical results.
18 "Untersuchung der Frage ob die Erde in ihrer Umdrehung urn die Achse, wodurch sie die Abwechselung des Tages und der Nacht hervorbringt, einige Veränderung seit den ersten Zeiten ihres Ursprunges erlitten habe, &c."Kant's
'Sämmtliche Werke,' Bd. I. p. 178.
19 It will be understood that I do not wish to deny that the earth's rotation may be undergoing retardation.