NATURE 



26= 



THURSDAY, JULY 



1896. 



GEOLOGY FOR STUDENTS. 

 The Sltidcnfs Lyell ; a Mcinunl of Elementary Geology. 

 Edited by John W. Judd, C.B., LL.D., F.R.S., Pro- 

 fessor of Geology, and Dean of the Royal College 

 of Science. Svo. I'p. xxiv + 635. (London : John 

 Murray, 1896.) 

 , 4^1 "HERE are plants so deep-rooted in their native 

 -I- soil that time seems practically powerless to 

 eradicate them, and even when razed to the ground, 

 they will yet spring up again, from their tenacious hold 

 in the heart of the earth beneath. 



Thus it is with the teachings of Lyell ; they have taken 

 so strong a hold upon the minds of English geologists, 

 that although the great historian of our science has been 

 dead since 1875, yet his writings still illumine the path, 

 and serve to guide full many a student who was unborn 

 when Lyell died. 



For the great " Principles of Geology," the inception of 

 which takes us back to a far earlier period than the first 

 edition of the " Student's Elements of Geology," indeed 

 to more than si.vty years ago, are still the guiding 

 "principles" along which the great lines of geological 

 thought continue to flow at the present day. 



It is true that from 1858 Lyell became a thorough 

 convert to the Darwinian theory of evolution, and, in the 

 later editions of his works, he fully accepted the inevit- 

 able conclusions which these views involved ; yet so far 

 from weakening his hold on geological thought, the very 

 openness of his mind proved him to be a teacher worthy 

 to be followed and trusted, one who was able to accept 

 new impressions and to advance, even in later life, along 

 new lines of scientific thought. 



In the work before us, we have embodied not only 

 the survival of all that is best and fittest of Lyell's teach- 

 ings, both in his " Elements " and " Principles," but also 

 there has been superadded to the original work — by a 

 species of " grafting " upon the parent Lyellian " stock " 

 — a vigorous shoot from a new root— that of Prof Judd, 

 representing the later school of geology, as carried on 

 in the Royal College of Science, South Kensington, 

 formerly the Royal School of Mines, where, year after 

 year, so many students have been trained to become 

 geologists and to go forth to convert the wilderness into 

 paying gold-fields, or to make geological maps of our 

 colonies all over the world. 



But much as this has added to the usefulness and 

 up-to-dateness of the " Student's Lyell," we are reminded 

 that other great "medicine-men" in geology have not 

 hesitated to lend their aid to keep alive the school of 

 Lyellian principles ; and we may record that Profs. 

 P. M. Duncan and T. G. Bonney, Mr. Etheridge, Prof 

 Rupert Jones, and Dr. W. F. Hume, have all helped to 

 make this volume what it is to-day, a most useful and 

 handy student's text-book of geology. 



In spite of the expansion of the text, and the intro- 

 duction into it of more than one hundred new illustra- 

 tions, it has nevertheless been found possible, by using 

 smaller type for Certain portions, to avoid increasing the 

 bulk or the cost of the volume. 

 NO. 1395, VOL. 54] 



Part i. embraces the introductory matter, such as the 

 history of the development of geological science, the 

 crust of the globe, and the nature of rocks and their 

 classification. 



The physical characters of the earth's crust, its 

 chemical composition, and the distribution of temper- 

 ature within the crust, has been entirely rewritten so as 

 to embrace the latest information obtained by the most 

 modern investigations. 



The general relations of the stratified rocks, dealing 

 also with the composition and classification of aqueous 

 deposits in general, occupy the next hundred pages. 



The following chapters treat of the chronology of 

 the aqueous rocks, commencing with the Tertiary — these 

 are disposed of in five chapters ; the Secondary rocks 

 occupy four more chapters, the Newer Pateozoic take 

 fifty-eight pages, and the Older Palseozoic era is con- 

 densed into forty-one pages. 



In dealing with the great series of aqueous or sedi- 

 mentary rocks, more than five hundred figures of 

 characteristic fossils are introduced into the text, and 

 everywhere the importance of palseontological evidence 

 as a means of determining the age of the rocks under 

 consideration is pointed out ; also the value of fossils as 

 showing the earliest appearance in time of the various 

 groups of living organisms is fully demonstrated. 



Chapter xxix. gives us a general review of the sedi- 

 mentary rocks ; and here the student is made to under- 

 stand that, as in the history of the human race, so it is 

 with the history of the earth. In each case the later 

 chapters are very fully and well preserved, and easily 

 read and understood ; but in both, the earlier portions 

 become more and more fragmentary — often whole 

 chapters are missing, and those which remain are 

 frequently torn and mutilated. 



" If we bear in mind how small must be the proportion 

 of the relics of plants and animals now existing, that 

 have any chance of being buried and preserved in the 

 accumulations now being formed in seas and lakes ; if 

 we consider how remarkable must be the combination of 

 circumstances conducing to the mineralisation of those 

 relics, and their preservation to a remote antiquity ; and 

 if we reflect upon the remoteness of the probability of 

 organisms, when buried and preserved by fossilisation, 

 being exposed at the surface and found by man — we 

 shall be on our guard against regarding the thousands 

 and hundreds of thousands of beautiful fossils which are 

 displayed in our museums, as representing more than a 

 very small fraction indeed of the forms of life that have 

 once existed on the globe" (pp. 443). 



Part iii. deals with volcanic phenomena and products, 

 with plutonic and metamorphic rocks, veins and metal- 

 liferous deposits. With this part of the work Prof Judd 

 must have felt, perhaps, the deepest interest, having made 

 a special study for years of the volcanic phenomena of 

 Europe, and given us in his volume on " Volcanoes " an 

 excellent vade mecum which every student must possess. 



It is interesting to know what line of thought Prof 

 Judd follows in reference to the assumed permanence of 

 oceanic and continental areas ; as this subject has greatly 

 disturbed the minds of geologists of late years. 



" From all that we know of the extreme slowness of the 

 upward and downward movements which bring about 

 even slight geographical changes, we may infer that it 



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