October io, 1901] 



NA TURE 



575 



THEORETICAL EXPLANATIONS OF 

 GEOLOGICAL FACTS. 

 Essai if line E.iplioiiioii par les Causes actitelles de la 

 Partie tMorique de la Geologic. Par H. Hermite. 

 Pp. 115. (Neuchatel ; Attinger, 1901.) 



M HERMITE believes that the facts of geology 

 • admit of much simpler theoretical explanations 

 than they have hitherto received. Whether his sub- 

 stitutes will be generally adopted is, we think, open to 

 question ; but as it would be a lengthy business to criticise 

 them in detail we must restrict ourselves to a brief out- 

 line of their leading features. Mountain-making is not, 

 as is generally thought, the result of a cooling of the 

 liquid earth's interior, for that is not in accord with the 

 theory of heat. It is caused thus : — The crust is very 

 flexible. Materials deposited upon it produce a down- 

 ward movement in that part with a corresponding up- 

 ward one in another, so the ocean basins are constantly 

 sinking and the continents rising. This upward move- 

 ment is concentrated on the periphery of the basins, 

 where the strata are bent, strained, and finally fractured. 

 Motion is converted into heat and the temperature of 

 this zone Is elevated. It then communicates heat to. the 

 adjacent ocean, and thus increases evaporation. That 

 results in a heavier rainfall. The precipitated water 

 works down into the rising land, thus cooling it, and pro- 

 ducing of course the greatest effect nearest to the surface. 

 So the rise of temperature observed in sinking wells, &c., 

 is due to a local cooling rather than to the cause 

 usually assigned. That the consequence of mountain- 

 making is abundant rain is proved by the prevalence 

 •of sandy deposits in the earliest geological ages. 

 Another consequence is that periods of extensive and 

 rapid deposit of detritus are succeeded by others of slow 

 and regular sedimentation. M. Hermite passes on to 

 explain the occurrence of the warm era with which the 

 earth's history began, and the glacial epoch of its later 

 days. Crust cohesion, he says, was great in early times, 

 so more material was needed to make it sink ; and thus 

 the rise of temperature of the basins was greater. 

 Evaporation was thereby increased and the whole surface 

 covered with a veil of mist, resulting in a mild, uniform 

 climate. But the heavy rains penetrating into the 

 crust ultimately chilled it, and the streams which they 

 produced cooled the ocean, till things returned to their 

 former condition. As the cohesion afterwards became 

 gradually less, this universal, warm, damp atmosphere 

 did not recur, and the loss of heat by radiation yaxe 

 rise to the seasons. But earth movements were augmented 

 about the time of the passage of the Tertiary into the 

 Quaternary, and led to precipitation which supplied the 

 snow for the great glaciers. Thus this epoch was brought 

 to an end rather by the diminished warmth of the ocean 

 waters than by a rise of the general air temperature. At 

 the present day the great glaciers of the Polar regions are 

 largely fed by the water emitted from volcanoes. The 

 Carboniferous period seems to have been a turning 

 point in the history of the globe ; for the crust up to 

 that time was less fissured, and so was not chilled by 

 the penetrating water ; hence the high temperature of 

 the seas kept the carbonic acid in the atmosphere. 

 But after that became fixed in the form of coal the 

 NO. 1667, VOL. 64] 



present conditions became possible. M. Hermite, we 

 think, is not likely to get his theory adopted by geologists 

 until he shows in more detail that it will harmonise 

 with the facts ; for he usually contents himself with 

 vague statements, which read like his impressions of 

 books. .\lso, when he plays havoc with the names of 

 fossils {e.g.. Rhinoceros, Thycorinus, for R. Tichorhinus), 

 and attributes the cirques and gorges of mountain 

 regions, with the canons of more level districts, to the 

 action of subterranean water, we feel that he is making a 

 possible exception a general rule, and we cannot help 

 doubting whether he has any practical knowledge of the 

 science. In fact, much of his geology seems on a par 

 with his statement (p. 29) that the volume of a series of 

 spherical shells increases as the cube of their radii. 



OUR BOOK SHELF. 



La Geologic. Par H. Guede. (Biblioth^que des 



Sciences Contemporaines.) Pp. 724. 151 figures 



intercalees dans le texte. (Paris : Schleicher Freres, 



1901.) 



In his very modest preface, the author of this volume 



disclaims any idea of adding to the accumulated mass of 



geological facts or of advancing new theories to account 



for them. His object is to present, in a lucid manner, a 



summary of acknowledged facts and generally received 



theories, following the encyclopiedic treatise of M. de 



Lapparent, and to do so in such a way as to make 



the subject of interest to the general reader, while 



avoiding the claptrap style of certain so-called popular 



works. 



In a task of this kind there is not much opportunity for 

 originality of treatment, and the author wisely follows 

 the general plan of geological treatises in discussing first 

 the causes at present in operation in the earth's crust, 

 secondly the changes in the earth's surface features, 

 thirdly the internal forces at work within the earth's 

 crust, and fourthly the evolution of the earth. In his 

 classification of the geological periods, the author follows 

 most French writers in treating the Quaternary era as 

 the equivalent of the Tertiary, Secondary and Primary 

 eras, a plan which is not without inconvenience to the 

 student. The illustrations of the book appear to be all 

 original, and are of a very simple character — indeed, 

 nothing more than transcripts of such rough sketches as 

 a teacher would draw upon the blackboard. While this 

 plan has the advantage of enabling the teacher to 

 emphasise the essenlial features in the sections and 

 fossils he refers to — and these are often missed in more 

 elaborate picture-illustrations — it is in some cases 

 manifestly inadequate for teaching purposes. Thus the 

 reader of this work would have no idea of the characters 

 of the rocks described when seen in thin sections under 

 the microscope. On the whole, however, the author may 

 be congratulated on having produced, within a very 

 moderate compass, a clear and exact exposition of 

 geological science. 



Farm Poidfry. By G. C. Watson. Pp. x -f- 341. Illus- 

 trated. (New York : The Macmillan Company, 1901 ; 

 London : Macmillan and Co., Ltd.) Price 5^-. net. 

 This popular sketch of poultry farming is a very useful 

 addition to the Rural Science Series. Mr. Watson has 

 written for practical men, and gives working details on 

 every part of his subject, but he has at the same time 

 written in a really scientific spirit. Scientific terms are, 

 indeed, entirely avoided ; the language is clear and 

 simple ; but the principles which underlie good practice 

 are in every case brought to the front, so that a rational 



