86 Reviews — Wallace's Island Life. 



admits in Chapter VI., very generally held. Nor are these views 

 confined to such speculations as those of a late President of the 

 Geological Society of Liverpool. They are still held, to a certain 

 extent, b}'^ no less an authorit}^ than Professor Huxley, who writes 

 (Nature, Nov. 4, 1880) : " There is nothing, so far as 1 am aware, in 

 the biological or geological evidence at present accessible, to render 

 untenable the hypothesis that an area of the mid-Atlantic or Pacific 

 sea-bed as big as Europe should have been upheaved as high as 

 Mont Blanc, and have subsided again, any time since the Palseozoic 

 epoch, if there were any grounds for entertaining it." Thus the 

 believers in the possibility of an Atlantis, notwithstanding the 

 severitj? of our author's remarks (p. 398), may take comfort in the 

 fact that Prof. Huxley deems such a thing possible, though he does 

 not say that the event ever took place. The business of geologists 

 is not so much to speculate on possibilities as to weigh the available 

 evidence, and nothing can be clearer than the fact that the Jurassic, 

 Lower Cretaceous, and Tertiary deposits, in our own country at least, 

 are more or less of a shallow water or marginal chai'acter ; but when 

 Prof. Huxley, some three-and-twent}'^ years ago. spoke of Atlantic 

 mud as " modern chalk," the converse of this proposition was imme- 

 diately taken for granted, viz. that the chalk must have been an 

 abyssal deposit. Thus this latter supposition strongly favoured the 

 then prevailing doctrine of the secular interchangeability of the 

 great land and water areas. To combat this notion the author 

 devotes several pages, and he certainly has the authority of Sir 

 "VVyville Thompson in support of his introductory statement, " That 

 few of the rocks known to geologists correspond exactly to the 

 deiDOsits now forming at the bottom of our great oceans." 



Still, the origin of chalk is a great puzzle, and some of Mr. 

 Wallace's statements are likely to lead to much discussion. Some- 

 times, indeed, he seems to advance arguments against his own 

 hypotheses, as, for instance, when he claims for his great central sea 

 the depth of a few thousand feet, and immediately quotes S. P. 

 Woodward to the effect that Ammonites, etc., were limited to depths 

 not exceeding 180 feet. We are far from saying, however, that even 

 these statements are essentially irreconcilable. There are large 

 vertical regions of the chalk singularly free from Cephalopoda, and 

 though, perhaps, not much of the sea in which chalk was deposited 

 ever attained a depth of a few thousand feet, yet a depth of several 

 hundreds — say even a thousand — might be sufficient to prevent the 

 accumulation of any notable quantity of Ammonite remains. 



The composition of chalk is also an enigma, for Foraminifera 

 form only a small part of it. On the strength of the Faxoe beds in 

 Denmark being highl}'- coralline, he observes, " We have a clear 

 indication of the source whence the white calcareous mud was 

 derived which forms the basis of chalk." This is a bold assumption. 

 In the first place, there are no regular reef-builders at Faxoe, the 

 principal species being a Caryophjllia. Secondly, Lyell (Tr. Geol. 

 Sbc. vol. V. p. 248) expresslj^ says, " There are patches of coral 

 cemented together by white chalk, but with these exceptions no 



