290 



NATURE 



[Fed. I, 1877 



to the memories of our readers— and ia doing so we shall 

 dwell more particularly on such as, through recent dis- 

 coveries or controversies, have acquired especial interest 

 at the present day. 



Every explorer who, since the publication of the " Ob- 

 servations on Volcanic Islands," has been called upon to 

 investigate districts containing extinct volcanos, has been 

 greatly aided by the valuable store of facts and sugges- 

 tions contained in that work. We very much doubt, how- 

 ever, whether some of the interesting questions discussed 

 in it — and we more especially refer to those relating to 

 the nature and origin of the banded structure in lavas, 

 with the light which these are calculated to throw on the 

 difficult problem of the cause of foliation in rocks — have 

 received that amount of attention from geologists, of which 

 they are certainly deserving. 



The proofs of the long-continued elevation of the shores 

 of South America for thousands of miles, and to the height 

 of many hundreds of feet, yet unattended with marked 

 disturbances of the strata, the gradual disappearance of 

 every trace of organism in rocks which once abounded 

 with them, the survival of a most remarkable fauna of 

 gigantic vertebrates to post-tertiary times, and its seem- 

 ingly sudden extinction at a very recent period — these are 

 some among the many interesting facts described in the 

 second part of the work which are of especial value to 

 geologists seeking to interpret the records of the past. 

 Mr. Darwin's observation of an admixture of Jurassic 

 and Cretaceous types of life in the same deposits in South 

 America have acquired fresh significance now that the 

 United States geologists have shown that ammonites 

 range up into the tertiary strata, and that Dr. Waagen has 

 described ammonites, goniatites, and ceratites, occurring 

 in India, in the same bed with several carboniferous spe- 

 cies of brachiopods. Now, too, that so much has been 

 done by Dana, Le Conte, and others, in determining 

 the mode of origin of the Rocky Mountains, and the 

 part played by the volcanic outbursts which occurred 

 simultaneously with the mountain-forming movements, 

 Mr. Darwin's clear descriptions of the sections noticed 

 by him in his traverses of the chain of the Andes will be 

 referred to with fresh interest by geologists : and the 

 comparison of phenomena displayed in distant parts of 

 the same great chain is highly suggestive. But space 

 fails us to refer to even a tithe of the points of interest 

 which we have noted in our reperusal of this valuable 

 work. 



A striking characteristic of all Mr. Darwin's writings, 

 and one which is very eminently displayed in the work 

 before us, is his scientific candour. Like his teacher and 

 friend, the late Sir Charles Lyell, he never forgets in his 

 discussions to look at all sides of the questions before him, 

 and to give the fullest expression and weight, alike to the 

 difficulties which he himself detects, and to arguments 

 which opponents may have advanced. With superficial 

 readers this peculiarity in the writings of Lyell and Dar- 

 win has apparently very unjustly detracted from their 

 merits ; and we are sometimes amused by finding critics 

 boldly parading as their own, objections which it is per- 

 fectly clear that only the candour of the authors has 

 permitted them to rehearse, but which their own know- 

 ledge has not sufficed to enable them to understand or to 

 make adequate use of. 



Perhaps at no period in the history of the science have 

 the great facts of geology suffered so much distortion 

 from the works of pseudo-scientific writers — through 

 which media alone science is too often, alas ! transmitted 

 to the general public — than at present. These writers 

 selecting a few isolated and imperfectly understood facts, 

 in bold defiance or lamentable ignorance of a thousand 

 unmistakable and clearly established principles, proceed 

 to build up the most elaborate hypotheses. We cannot 

 therefore help regarding the republication of Mr. Dar- 

 win's " Geological Observations " as a most opportune 

 event. The able geologist, De la Beche, many years ago 

 wrote a charming little book entitled " How to Observe 

 in Geology." To those anxious to learn this most import- 

 ant art at the present time, we would recommend as a 

 model — since example is better than precept — the work 

 now before us. The careful study of the clear and minute 

 descriptions of geological phenomena, and the following 

 step by step of the fair and cautious discussion of facts 

 and arguments contained in this book can scarcely fail 

 indeed to teach the reader something which is even more 

 valuable than "how to observe," namely, how to reason 

 in geology. John W. Judd 



TWO ''CHALLENGER" BOOKS 



Log Letters from the " Challenger^' By Lord George 

 Campbell. (London : Macmillan and Co., 1876.) 



The Cruise of Her Majesty s Ship " Challenger." By 

 W. J. J. Spry, R.N. With Map and Illustrations. 

 (London : Sampson Low and Co., 1876.) 



IT was to be expected that with so carefully-selected 

 and intelligent a staff, both naval and civilian, on 

 board, the cruise of the Challenger would be productive 

 of something more than the official literature. It will 

 have been seen from the " Preamble " which we recently 

 published {antea, p. 254) that it must necessarily take a 

 long time to arrange the abundant scientific results that 

 have been obtained, and the complete official accounts 

 may not be in the hands of the public for years. The 

 Report on the Austrian Novara Expedition has taken 

 seventeen years' serious labour to complete ; but we hope 

 to be in possession of the Challenger Reports in a much 

 less space of time. Meantime many readers will be glad 

 to have in a handy form a general account of the work 

 which the expedition has done, and some details concern- 

 ing the incidents of the long cruise and the many places 

 which the ship visited. From either of the books before 

 us such information may be obtained. 



There is a wide difference, however, between the charac- 

 ters of the two works. Lord Campbell's is by no means an 

 attractive book at first sight. It is a big, plain, heavy-looking 

 volume, with a large page well filled with type, enormous 

 paragraphs of sometimes half-a-dozen pages in length, and 

 with not a single picture. One is apt to sigh at first at being 

 compelled to read it, but after perusing a few sentences the 

 reader " puts on the garment of praise for the spirit of 

 heaviness," and finds the real difficulty to be to stop. 

 Lord Campbell's pages bear all the marks of being 

 genuine letters, written with no thought of a public before 

 him, and only for the entertainment of those to whom 

 they were sent. He has evidently not " got up " his sub- 

 ject at all, the information he conveys being almost 



