January 25, 1894] 



NA TURE 



287 



tract of the ether vapours in the Soxhlet apparatus is 

 wrongly described, and the treatment of the subject of 

 soil examination is crude. 



Although it is not difficult to thus indicate many points 

 with which a critic in this country may find fault, the 

 work may with profit be consulted on many subjects, and 

 none with greater advantage than that of Food. 



The book is capitally printed and bound in two handy- 

 sized volumes. 



THE LATEST TEXT-BOOK OF GEOLOGY. 

 Text-Book of Geology. By Sir Archibald Geikie, Director- 

 General of the Geological Survey of Great Britain and 

 Ireland. Third Edition, revised and enlarged. (Lon- 

 don : Macmillan and Co., 1893.) 

 T T goes very much against the grain, for it savours of 

 ingratitude, to begin by picking holes in a book that 

 has been a trusted companion, that has proved itself 

 worthy of trust, and to which I have been so largely in- 

 debted, as the volume before me. But the strictures I 

 feel bound to make are not very severe, and the blots I 

 cannot help noticing do not impair seriously the value 

 of the work- -do not, indeed, detract at all from its use- 

 fulness in the case of a large number of readers. 



The first point on which I have always differed from 

 the author is this. In Book i., which deals with the 

 cosmical aspects of geology, we are introduced to some 

 of the darkest and most unsettled problems that arise 

 when we concern ourselves with the earth's history ; the 

 stability of its axis, the degree of its rigidity, the causes 

 of the changes of climate which have occurred in bygone 

 days. Besides their obscurity these points have not a 

 little in common, and much may be said in favour of 

 grouping them together. But when we find it stated in 

 the preface that the method of treatment adopted is one 

 which the author has found, while conducting his geo- 

 logical class, to afford the student a good grasp of the 

 general principles of the science, it is hardly possible to 

 avoid doubting the wisdom of bringing them in at so 

 early a stage. To do this is to run counter to that prime 

 canon of teaching, which bids us start with the concrete, 

 simple, and known, and lead thence up to the abstract, 

 complex, and hypothetical. To the advanced student, 

 who has already made the acquaintance of these un- 

 settled points, such a summary as we have here of what 

 has been done towards their solution is most valuable ; 

 but it is rather strong meat for the beginner. On just 

 the same grounds I would object to putting in the fore- 

 front speculations as to the state of the earth's interior 

 or her age. Something may be said in favour of an 

 early notice of the nebular hypothesis, for it looks like 

 beginning at the beginning. But to do this successfully 

 we must have some certain knowledge of what the 

 beginning was, and this we assuredly have not in the 

 case of the earth. So greatly do I differ from the author's 

 view as expressed in the preface that I always recom- 

 mend students to omit large portions of Books i. and ii. 

 on their first reading. In the same connection one may 

 note that, on the principle that the father comes before 

 the children, hypogene action precedes epigene action in 

 Book iii. But on grounds already stated, I should be 

 inclined to reverse the order. 



NO. 1265, VOL. 49] 



Further, while all that style could do to render the 

 work attractive has been done, I have found that the 

 arrangement of its matter tends to render it at times 

 rather hard reading. It is somewhat irritating, when 

 you have begun to grow warm on some subject and want 

 to know everything that is known about it, to be told 

 that no more can be said here, but that some information 

 has been given in a previous book, and that the subject is 

 further discussed in a subsequent book. It is no great 

 hardship to have to turn backwards or forwards, though a 

 little hunting may be required to find the exact passage 

 sought ; yet these cross references do act as a check on 

 the even flow of one's thought, and they occur pretty 

 frequently. A little more elasticity and a little less con- 

 sistency may be desiderated. Take the case of metamor- 

 phism. In Book ii. part 7, section iii. we have a descrip- 

 tion of the chief varieties of metamorphic rocks ; then, 

 under the head of Dynamical Geology, in Book iii., 

 instances of the changes produced by metamorphism ; 

 lastly, in Book iv., which treats of the architecture of 

 the earth's crust, we are told of some additional meta- 

 morphic changes and of the processes by which meta- 

 morphism is brought about. It is difficult to see why the 

 last two sections should have been so widely separated 

 for the process of metamorphism, specially of regional 

 metamorphism, is a dynamical operation. It would have 

 been a convenience and would have saved some repeti- 

 tion, to have had all these sections in continuous 

 sequence ; and it is instructive to notice how impossible 

 is rigid adherence to systematic arrangement, for even 

 in the descriptive section there are constant anticipations 

 of the dynamical problems which are treated more fully 

 later on. 



There are other cases in which, for a similar reason, it 

 will be found troublesome to gather into a connected 

 whole all that the book has to tell on a specific subject ; 

 but the trouble will be well repaid, for it is a book almost 

 exhaustive in its fulness, copiously illustrated, lucid in its 

 descriptions, and a model of English in style. As an 

 illustration of its thoroughly practical character, we may 

 point to the minute directions on the subject of fossil- 

 collecting at the end of Book v. On some of the more 

 recondite and obscure problems of geology, the author 

 has wisely refrained from attempting to decide between 

 rival hypotheses ; but he has summarised the more im- 

 portant speculative solutions that have been put forward, 

 and has given such full references to the papers in which 

 these appear, that the reader, who is so minded, can 

 easily follow out the questions for himself. Indeed, 

 throughout what may be called the physical side of 

 geology, the book is a most exhaustive and trust- 

 worthy compendium, such as could be produced only by 

 one who has a wide acquaintance with the literature of the 

 subject, and who has also been brought face to face with 

 what he describes by life-long and varied work in the field. 



When we come to stratigraphical geology, it behoves 

 the critic to be wary in his judgments. To treat this 

 satisfactorily seems to me to be the most trying ordeal to 

 which the writer of a text-book can be subjected. At the 

 very threshold we are met with one of the most perple.x- 

 ing of geological problems, when we are called upon to 

 decide between the rival claims of contemporaneity and 

 homotaxis. The subject is discussed at some length by 



