THE SCOTTISH SCHOOL OF GEOLOGY*

I.

FOR the first time in the history of University Education in Scotland, we are to-day met to begin the duties of a Chair specially devoted to the cultivation of Geology and Mineralogy. Though Science is of no country nor kin, it yet bears some branches which take their hue largely from the region whence they sprang, or where they have been most closely followed. Such local colourings need not be deprecated, since they are both inevitable and useful. They serve to bring out the peculiarities of each climate, or land, or people, and it is the blending of all these colourings which finally gives the common neutral tint of science. This is in a marked degree true of Geology. Each country where any part of the science has been more particularly studied, has given its local names to the general nomenclature, and its rocks have sometimes served as types from which the rocks of other regions have been classified and described. The very scenery of the country, reacting on the minds of the early observers, has sometimes influenced their observations, and has thus left an impress on the general progress of the science. As we enter to-day upon a new phase in the history of Geology among us here, it seems most fitting that we should look back for a little at the past development of the science in this country. There was a time, still within the memory of living men, when a handful of ardent original observers here carried geological speculation and research to such a height as to found a new, and, in the end, a dominant shool of Geology.

In the history of the Natural Sciences, as in that of Philosophy, there have been epochs of activity and then intervals of quiescence. One genius, perhaps, has arisen and kindled in other minds the flame that burned so brightly in his own. A time of vigorous research ensued, but as the personal influence waned, there followed a period of feebleness or torpor until the advent of some new awakening. Such oscillations of mental energy have an importance and a significance far beyond the narrow limits of the country or city in which they may have been manifested. They form part of that long and noble record of the struggle of man with the forces of nature, and deserve the thoughtful consideration of all who have joined or who contemplate joining in that struggle. I propose on the present occasion to sketch to you the story of one of these periods of vigorous originality, which had its rising and its setting at Edinburgh-the story of what may be called the Scottish School of Geology. I wish to place before you, in as clear a light as I can, the work which was accomplished by the founders of that school, that you may see how greatly it has influenced, and is even now influencing, the onward march of the science. I do this in no vainglorious spirit, nor with any wish to exalt into prominence a mere question of nationality. Science knows no geographical or political limits. Nor, though we may be proud of what has been achieved for Geology in this little kingdom, can we for a moment shut our eyes to the fact that these achievements are of the past, that the measure of the early promise at the beginning of this century has been but scantily fulfilled in Scotland, and that the state of the science among us here, instead of being in advance, is rather behind the time. And thus I dwell now on the example of our predecessors, solely in the hope that, realising to ourselves what that example really was, we may be stimulated to follow it. The same hills and valleys, crags and ravines, remain around us which gave these great men their inspiration, and still preach to us the lessons which they were the first to understand.

The period during which the distinctively Scottish School of Geology rose and flourished may be taken as included between the years 1780 and 1825-a brief half-century. Previous to that time Geology, in the true sense of the word, can hardly be said to have existed. Steno, indeed, more than a hundred years before, had shown, from the occurrence of the remains of plants and animals imbedded in the solid rocks, that the present was not the original order of things, that there had been upheavals of the sea into dry land and depressions of the land beneath the sea, by the working of forces lodged within the earth, and that the memorials of these changes were preserved for us in the rocks. Seventy years later, another writer of the Italian school, Lazzaro Moro, adopting and extending the conclusions of Steno, pointed to the evidence that the surface of the earth is every. where worn away, and is repaired by the upheaving power of * A Lecture delivered at the opening of the clas of Geology and Mineralogy in the University of Edinburgh, by Archibald Geikie, F.R.S., Nov. 6, 1871.

earthquakes, but for which the mountains and all the dry land would at last be brought beneath the level of the waves.

But none of these desultory researches, interesting and important though they were as landmarks in the progress of science, bore immediate fruit in any broad and philosophic outline of the natural history of the globe. Men were still trammelled by the belief that the date and creation of the world and its inhabitants could not be placed further back than some five or six thousand years, that this limit was fixed for us in Holy Writ, and that every new fact must receive an interpretation in accordance with such limitation. They were thus often driven to distort the facts or to explain them away. If they ventured to pronounce for a natural and obvious interpretation, they laid themselves open to the charge of impiety and atheism, and might bring down the unrelenting vengeance of the Church.

Such was the state of inquiry when the Scottish Geological School came into being. The founder of that school was James Hutton-a man of a singularly original and active mind, who was born at Edinburgh in 1726, and died there in 1797. Educated for the medical profession, but possessed of a small fortune, which gave him leisure for the pursuit of his favourite studies, he eventually devoted himself to the study of Mineralogy. But it was not merely as rare or interesting objects, nor even as parts of a mineralogical system, that he dealt with minerals. They seemed to suggest to him constant questions as to the earlier conditions of our planet, and he was thus gradually led into the wider fields of Geology and Physical Geography. Quietly working in his study here, a favourite member of a brilliant circle of society, which included such men as Black, Cullen, Adam Smith, and Clerk of Eldin, and making frequent excursions to gather fresh data and test the truth of his deductions, he at length matured his immortal "Theory of the Earth," and published it in 1785. Associated with Hutton, rather as a friend and enthusiastic admirer than as an independent observer, was John Playfair, Professor of Natural Philosophy in this University, by whose graceful exposition the doctrines of Hutton were most widely made known to the world. His classic "Illustrations of the Huttonian Theory" is one of the most delightful books of science in our language-clear, elegant, and vivacious-a model of scientific description and argument, which I would most earnestly recommend to your notice. Sir James Hall, another of this little illustrious band, had one of the most inventive minds which have ever taken up the pursuit of science in this country. His merits have never yet been adequately realised by his countrymen, though they are better appreciated in Germany and in France. He was in fact the founder of Experimental Geology, since it was he who first brought geological speculation to the test of actual physical experiment. This he accomplished in a series of ingenious researches, whereby he corroborated some of the disputed parts of the doctrines of his master, Hutton. These were the three chief leaders of the Scottish school; but to their number, as worthy but less celebrated associates, we must not omit to add the names of Mackenzie, Webb Seymour, and Allan.

It would lead me far beyond the allotted hour to attempt any adequate summary of the work achieved by each of these early pioneers of the science. It will be enough for my present purpose if I try to sketch to you what were the leading characteristics of this Scottish School, and what claim it has to be remembered, not by us only, but by all to whom Geology is the subject either of serious study or of pleasant recreation.

Born in a "land of mountain and flood," the geology of the Scottish School naturally dealt in the main with the inorganic part of the science, with the elemental forces which have burst through and cracked and worn down the crust of the earth. It asked the mountains of its birthplace by what chain of events they had been upheaved, how their rocks, so gnarled and broken, had come into being, how valleys and glens had been impressed upon the surface of the land, and how the vari: as strata through which these wind had been step by step built up. It encountered no rocks, like those which had arrested the notice of the early Italian geologists, charged with fossil shells, and corals, and bones of fish, such as still lived in the adjoining seas, and which at once suggested the former presence of the sea over the land. Neither did it meet with deposits showing abundant traces of ancient lakes, and rivers, and land-surfaces, each marked by the presence of animal and plant remains, like those which set Steno and Moro thinking. The rocks of Scotland are as a whole unfossiliferous. It was, therefore, only with the records of physical events, unaided by the testimony of organic remains, that the Scottish geologists had to deal. Their task was to unravel the

complicated processes by which the rocky crust of the earth has been built up, and by which the present varied contour of the earth's surface has been produced,—to ascertain, in short, from a study of the existing economy of the world, what has been the history of our planet in earlier ages.

Hitherto, while men had been accustomed to believe that the earth was but some 6,000 years old, they sought in the rocks beneath and around them evidence only of the six days' creation or of the flood of Noah. Each new cosmological system was based upon that belief, and tried in various ways to reconcile the Biblical narrative with fanciful interpretations of the facts of Nature. It was reserved for Hutton to declare, for the first time, that the rocks around us can never reveal to us any trace of the beginning of things. He too first clearly and persistently proclaimed the great fundamental truth of Geology, that in seeking to interpret the past history of the earth as chronicled in the rocks, we must use the present economy of nature as our guide. In our investigations, no powers, he says, ployed that are not natural to the globe, no action to be admitted of except those of which we know the principle. Nor are we to proceed in feigning causes when those appear insufficient which occur in our experience.' This was the guiding principle of the Scottish School, and through their influence it has become the guiding principle of modern Geology.

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There were two directions in which Hutton laboured, and in each of which he and his followers constantly travelled by the light of the present order of nature-viz., the investigation of (1) changes which have transpired beneath the surface and within the crust of the earth, and (2) changes which have been effected on the surface itself.

I. That the interior of the earth was hot, and that it was the seat of powerful forces, by which the solid rocks could be rent open and wide regions of land be convulsed, were familiar facts, attested by every volcano and earthquake. These phenomena had been for the most part regarded as abnormal parts of the system of nature; by many writers, indeed, as well as by the general mass of mankind, they were looked upon as Divine judgments, specially sent for the punishment and reformation of the human species. To Hutton, pondering over the great organic system of the world, a deeper meaning was necessary. He felt, as Steno and Moro had done, that the earthquake and volcano were but parts of the general mechanism of our planet. But he saw also that they were not the only exhibitions of the potency of subterranean agencies, that in fact they were only partial and perhaps even secondary manifestations of the influence of the great internal heat of the globe, and that the full import of that influence could not be understood unless careful study was also given to the structure of the rocky crust of the earth. Accordingly, he set himself for years patiently to gather and meditate over data which would throw light upon that structure and its history. The mountains and glens, rivervalleys and sea-coasts of his native country, were diligently traversed by him, every journey adding something to his store of materials, and enabling him to arrive continually at wider views of the general economy of nature. At one time we find him in a Highland glen searching for proofs of a hypothesis which he was convinced must be true, and, at their eventual discovery, breaking forth into such gleeful excitement that his attendant gillies concluded he must certainly have hit upon a mine of gold. At another time we read of him boating with his friends Playfair and Hall along the wild cliffs of Berwickshire, again in search of confirmation to his views, and finding, to use the words of Playfair, "palpable evidence of one of the most extraordinary and important facts in the natural history of the earth."

As a result of his wanderings and reflection, he concluded that the great mass of the rocks which form the visible part of the crust of the earth was formed under the sea, as sand, gravel, and mud are laid there now; and that these ancient sediments were consolidated by subterranean heat, and, by paroxysms of the same force, were fractured, contorted, and upheaved into dry land. He found that portions of the rock had even been in a fused state; that granite had erupted through sedimentary rocks; and that the dark trap-rocks or "whinstones" of Scotland were likewise of igneous origin.

When the sedimentary rocks were studied in the broad way which was followed by Hutton and his associates, many proofs appeared of ancient convulsions and re-formations of the earth's surface. It was found that among the hills the strata were often on end, while on the plains they were gently inclined; and the

* Hutton's "Theory of the Earth," i. p. 160; ii. p. 549.

inference was deduced by Hutton that the former series must have been broken up by subterranean commotions before the accumulation of the latter, which was derived from its débris. He conjectured that the later rocks would be found actually resting upon the edges of the older. His search for, and discovery of, this relation at the Siccar Point, on the Berwickshire coast, are well described by his biographer Playfair, who accompanied him, and who, dwelling on the impression which the scene had left upon him, adds: "The mind seemed to grow giddy by looking so far into the abyss of time; and while we listened with earnestness and admiration to the philosopher who was now unfolding to us the order and series of these wonderful events, we became sensible how much farther reason may sometimes go than imagination can venture to follow." Sir James Hall afterwards, by a series of characteristically ingenious experiments, showed how the rocks of that coast-line may have been contorted by movements in the crust of the earth under great superincumbent pressure.

Hutton was the first to establish the former molten condition of granite, and of many other crystalline rocks. He maintained that the combined influence of subterranean heat and pressure upon sedimentary rocks could consolidate and mineralise them, and even convert them into crystalline masses. He was thus the founder of the modern doctrines of metamorphism regarding the gradual transformation of marine sediments into the gnarled and rugged gneiss and schist of which mountains are built up. Let me quote the eulogium passed upon this part of his work in an essay by M. Daubrée, which eleven years ago was crowned with a prize by the Academy of Sciences at Paris :-" By an idea entirely new, the illustrious Scottish philosopher showed the successive co-operation of water and the internal heat of the globe in the formation of the same rocks. It is the mark of genius to unite in one common origin phenomena very different in their nature." "Hutton explains the history of the globe with as much simplicity as grandeur. Like most men of genius, indeed, who have opened up new paths, he exaggerated the extent to which his conceptions could be applied. But it is impossible not to view with admiration the profound penetration and the strictness of induction of so clear-sighted a man, at a time when exact observations had been so few, he being the first to recognise the simultaneous effect of water and heat in the formation of rocks, in imagining a system which embraces the whole physical system of the globe. He established principles which, in so far as they are fundamental, are now universally admitted.” (To be continued)

SCIENTIFIC SERIALS

Annalen der Chemie und Pharmacie, clix., for July, opens with a concluding communication "On the constitution of the twice substituted benzenes," by E. Ador and V. Meyer. The authors converted sulphanilic acid into bromobenzine-sulphonic acid, and fused the potassium salt of this acid with potassic hydrate. The dihydroxylbenzine produced was found to be resorcin; Meyer and others have proved that resorcin belongs to the I: 4 series, and therefore sulphanilic acid must also be regarded as containing the SO,H and NH, in the places 1 and 4 respectively. Sulphanilic acid treated with nitrous acid yields a diazo-derivative CHAN2SO, this on boiling with water is converted into phenolsulphonic acid, which was found to be identical with Kekule's paraphenolsulphonic acid. At the end of the communication, a valuable table of the twice substituted benzines, showing the place of attachment of the second substituted group is given; it however differs in some respects from the arrangement of other chemists. Ernst and Zwenger have prepared ethyl and amyl gallates by passing hydrochloric acid through a boiling solution of gallic acid in the anhydrous alcohols; at present they have not succeeded in follows preparing the methyl gallate.-A very exhaustive paper from borax," by A. Knop, in which the crystallisation of phos"On some substances crystallised from microcosmic salt and phostannic, phosphozirconic, and phosphoniobic acids from microcosmic salt, and of stannic acid, zirconic acid, noria, and niobic acid from borax are thoroughly discussed.-Lieben and boiling alcoholic potash on butyl cyanide, they find that the Rossi have prepared "normal valeric acid" by the action of valeric acid thus obtained does not agree in properties with either of the acids already known. They have also prepared normal amylic alcohol from the above acid, by heating the calcic valerate with calcic formiate, the valeric aldehyde being converted into amylic alcohol by the action of sodium amalgam. The alcohol

CHESTER

Society of Natural Science, October 25.-President, Rev. Canon Kingsley; treasurer, Mr. Kinsman; hon. secretary, Mr. Manning. The society is divided into three sections: (1) botany, (2) geology, (3) zoology; and numbers nearly 200 members. Mr. Alfred O. Walker read a paper on "Objects and Organisation of Local Natural History Societies."

read a paper

GLASGOW

Geological Society, October 19.—Mr. Edward A. Wünsch, vice-president, in the chair. The Annual Report and abstract of the accounts for past year showed the society to be in a flourishing condition. Mr. James Thomson, F.G.S., "On the Plagiostomous Fishes of the Coal Measures,' particularly Orthacanthus Dechenii Goldfuss. He observed that Prof. Agassiz, in his "Poissons Fossiles" published in 1837, described the genus Diplodus (sp. gibbosus and minutus) from specimens, chiefly of dissociated teeth, found in the English coal-fields. Subsequently, a well-preserved fish was discovered in Bohemia, and described in 1847 by Goldfuss, who named it Orthacanthus Dechenii. In 1848, Prof. Beyrich, of Berlin, described the same fish, and named it Xenacanthus Dechenii, founding on the fact that the spine had a greater similarity to Pleuracanthus than to Orthacanthus. At the meeting of the British Association in Glasgow in 1855, Sir Philip Egerton, from discoveries that had been made in the interval, pointed out that the spines of Pleuracanthus and the teeth of Diplodus belonged in fact to the same fish. The specimens from which Sir Philip proved this to the Association were obtained from Carluke and Edinburgh. In 1867 Prof Kner went carefully over the remains of such fishes in the museums of Dresden, Berlin, Breslau, and Vienna. Although none of the specimens found in these museums were complete, yet in some of them he found the teeth of Diplodus minutus of Agassiz in position, and from the external aspect of the fossils he accepted Goldfuss's generic name, Orthacanthus Dechenii. The specimen which Mr. Thomson now exhibited had been for many years in his collection, and had been provisionally named Pleuracanthus minutus. After a careful examination, however, of the microscopic structure both of the teeth and the sh green, he could find no relation between the structure of Pleuracanthus and that now exhibited. In the meantime he accepted Prof. Kner's identification, but thought it possible that the discovery of better-preserved specimens would show that the difference of structural character might be due to difference of sex, as he had found to be the case in the recent rays' jaws of Raia clavata, both male and female, with the teeth in position, exhibited in support of this view.

PARIS

Academy of Sciences, October 30. M. P. A. Favre read a continuation of his researches upon the thermal pheno. mena of electrolysis, containing an account of his investigations upon alkaline bases and sulphates; M. Wurtz presented the continuation of a paper, by M. G. Salet, on the spectra of phosphorus and of the compounds of silicium; and M. Le Verrier communicated a note by M. Diamilla-Müller, on a series of simultaneous magnetic observations which it is proposed to make in various parts of the surface of the globe, on the 15th of October, 1872. This note is accompanied by a table of the absolute magnetic declinations calculated for the above date, at a great number of places in all parts of the eastern hemisphere. -MM. Dumas and Chevreul and General Morin discussed the right of Daguerre to be regarded as the inventor of photography, and asserted the prior claims of Niepce de Saint-Victor.-M. Faye read the conclusion of his memoir on the history and present state of the theory of comets.-M. Delaunay pre en ed a note by M. G. Leveau, giving the elements of the planet Hera (103). A note was read by M. Barbe, on the uses of dynamite. -M. E. M. Raoult read a note on the transformation of dissolved cane-sugar into glucose, under the influence of light. The exposure lasted from May 12 to October 20.-M. Berthelot communicated the third part of his investigations of the ammoniacal salts, in which he discussed the reciprocal actions of the salts of ammonia and of the other alkalies.-A note was read by MM. A. Scheurer-Kestner and C. Meunier, on the composition and heat of combustion of two Welsh coals (from Bwlf and Powel.)-M. Daubrée communicated a paper on the deposit in which phosphate of lime has lately been discovered in the departments of Tarn-et-Garonne and the Lot.--M. A. Damour presented a note on an idocrase from Arendal, in Norway, con

taining an analysis of the mineral, and also an analysis of a garnet from Mexico.-M. E. Blanchard communicated a note by M. S. Jourdain, on the reproduction of Helix aspersa, in which the author described the arrangement of the reproductive organs and the mode in which their products are brought together.

BOOKS RECEIVED

ENGLISH-The Letters of J. B. Jukes: Edited by his Sister (Chapman and Hall).-A Handbook of the Mineralogy of Cornwall and Devon: J. H. Collins (Longmans).-A Manual of Anthropology, or Science of Man: C. Bray (Longmans).-Note-book of Practical and Solid Geometry: J. H Edgar (Macmillan).-The Admiralty Manual of Scientific Inquiry, 4th edition: Rev. R. Main (J. Murray).-Proceedings of the South Wales Institute of Engineers; Vol. vii, No. 2-4.-Insects at Home, being a popular account of British Insects: Rev. J. G. Wood (Longmans).

AMERICAN. Three and Four place Tables of Logarithmic and Trigonometric Functions: J. M. Peirce (Boston, Ginn Brothers).-Seaside Studies in Natural History; Marine Animals of Massachusetts Bay, Radiates: Elizabeth C. Agassiz and Alexander Agassiz (Boston, J. R. Osgood and Co.). FOREIGN (1hrough Williams and Norgate)-Lehrbuch der anorganischen Chemie: Dr. Th. Ph. Büchner; ite Abtheilung.-Wöhler's Grundriss der organischen Chemie: Dr. R. Fittig; 8te Auflage Die Zielpunkte der physikalischen Wissenschaft: E. Hagenbach.- Astronomische Tafeln u. Formeln Dr. C. F. W. Peters.

THURSDAY, NOVEMBER 16, 1871

NEW WORKS ON MECHANICS Lehrbuch der Mechanik in elementarer Darstellung mit Uebungen und Anwendungen auf Maschinen und BauConstructionen. Von Ad Wernicke. Vol. I. (Braunschweig, 1871. London: Williams and Norgate.) Lehrbuch der physikalischen Mechanik. Von Dr. Heinrich Buff. Vol. I. (Braunschweig, 1871. London : Williams and Norgate.)

WE

WERNICKE'S work is intended for pupils in the Prussian industrial schools (Gewerbeschulen). The first volume treats of Statics and Dynamics, leaving Hydromechanics for the second. According to the preface, students reading this work should be acquainted with elementary mathematics, including co-ordinate geometry, while a knowledge of the differential calculus is not required. From an English point of view, it is not desirable to draw the line between co-ordinate geometry and the calculus. Even in our universities, not twenty per cent. of the students are acquainted with co-ordinate geometry. It is to be regretted that the proportion is so small; that it is so, is due to the present preposterous system of classical education, that relic of the middle ages which is the bane of our schoolboy days. Almost all English students, however, who learn co-ordinate geometry, generally study both the differential and integral calculus before commencing mechanics. Now intelligent pupils like a text-book of mechanics in which they find scope for exercising all their mathematical knowledge; hence it would appear that for English purposes the line is drawn either too high or too low.

As to the manner in which Wernicke has executed his task, it would be hard to speak too favourably; and not; withstanding the point we have raised, we should hail an English translation as a valuable addition to our standard works on mechanics. One of the best features in the book is that it presents theoretical and practical mechanics not as two distinct subjects, but in that degree of combination which naturally belongs to them.

The first volume of Wernicke's work consists of 500 octavo pages, and is divided into three parts. Part I. discusses the Kinematics of a mathematical point, the inquiry being principally confined to space of two dimensions. The symbol j is here and throughout the work used to denote an acceleration for example, ja is the acceleration parallel to the axis of x. This notation (unfamiliar to English readers) has obvious advantages when the more appropriate language of the differential calculus cannot be employed. About fifty examples, many of a practical character, are appended to Part I. Among them is found (Ex. 31) a problem virtually requiring the integration of ". The solution given is necessarily roundabout and cumbrous, owing to the restraint which the author has imposed upon his use of mathematics. It may, indeed, be questioned whether a student who is not acquainted with the integral calculus could really

VOL. V.

The third part, which treats of the mechanics of a discusses the Composition and Equilibrium of Forces in space; some of the examples require a good deal of honest numerical work, others are well-known questions not involving friction. Chap. II. is on the Centre of Gravity; in this we do not notice much that is unusual, except the excellence of the illustrations. The examples contain problems on the centre of gravity of various useful areas and volumes, the theory of the arch, and many other subjects.

In Chap. III. we have a treatise upon Friction. We miss here an actual description and discussion of a series of experiments from which the laws of friction are established. This omission is to be regretted, because the laws are only approximate, and it is important for the pupil to have materials presented to him from which he can form his own estimate of their correctness. Intelligent pupils would have been pleased to find how true the laws are on the whole, and interested in noting the discrepancies. No good opportunity for introducing and discussing the results of experiments should have been lost in a work of this kind. With this exception, the force of friction has been treated in a manner worthy of its importance; we find its effect upon the various mechanical powers, upon toothed wheels and brakes, and in many other cases, treated in an excellent manner. Chap. IV., on the Motion of a rigid body, very properly commences with the exquisite kinematical theorems of Poinsot. D'Alembert's principle follows, and also a table of moments of inertia, which will be found a useful aid in recollecting these troublesome quantities.

Chap. V., on Elasticity and Rigidity, is certainly the best chapter in the book. Problems connected with the deflection of a beam are among the most interesting questions of mechanics. We have here an exceedingly careful dis cussion of this subject, not too much encumbered with formula. A large number of examples thoroughly worked illustrate this chapter. Every teacher of applied mechanics will find these examples invaluable; they are far better than those on the same subject in any other book with which we are acquainted.

Finally, in estimating the merits of this work, we must recollect that it is a manual for class instruction; it is not, nor does it profess to be, a comprehensive and original treatise, like the great work of Weisbach.

Buff's work, of which the first volume is before us, is of somewhat different character to that of Wernicke. It bears the same marks of painstaking thoroughness which characterise the better class of German works on science.

D