Revieics — Wallace's Island Life. 87 



portion of onr Oolitic rocks can less resemble ordinary chalk than 

 the stone of Faxoe." We may add that the undoubted coral muds 

 which have gone to form many of our Jurassic limestones yield a 

 very different kind of rock to any variety of chalk known to us. 

 Yet it must be admitted that Sorby, in his first address to the 

 Geological Society in 1879, says, "that very many of the minute 

 granules (of chalk) are identical in appearance with those derived 

 from aragonite shells and corals," and he further observes that, 

 though the more or less entire shells of Foraminifera form an 

 important constituent, " yet that other larger calcareous organisms 

 have probably yielded the greater part of the rock," When we quit 

 the basin of the North Sea for that of the S.W. of France, the 

 evidence for coral life is stronger, and the abundance of Eij)purites, 

 a relative of the reef-dwelling Cliama, also points in this direction. 



Whatever has been the origin of the composition of the peculiar 

 rock known as chalk, the fairest inference seems to be that the 

 conditions which produced it, in this country at least, were pelagic, 

 though by no means oceanic, and hence its existence gives no colour 

 to the notion of a great interchange of continent and ocean. Sir 

 Wyville Thompson is quite in accord with the author on this point 

 when he says {Nature, Nov. 1880), "The Chalk of the Cretaceous 

 period was not laid down in what we now consider deep water, and 

 its fauna, consisting mainly of shallow water forms, merely touches 

 the upper limit of the abyssal fauna." Prof. Geikie (quoted at 

 p. 94) is practically of the same opinion, when he says that during 

 the Cretaceous period " the Atlantic sent its waters across the whole 

 of Europe and into Asia, but they were probably nowhere more 

 than a few hundred feet deep." Unfortunately, in thus ignoring 

 the existence at this period of the Scandinavian and other highlands 

 of Old Europe, Prof. Geikie gives colour, perhaps unintentionally, 

 to the notion that the leading features of continents are less perma- 

 nent than the theory adopted by the author would lead us to suppose. 



This doctrine, viz. the permanence of continents and oceans, he 

 considers lies at the root of all our inquiries into the past changes of 

 the earth and its inhabitants, and it receives strong confirmation 

 from the evidence adduced by Darwin, who has observed that hardly 

 one truly oceanic island has been known to afford a trace of any 

 Paleozoic or Mesozoic formation, so that they have not preserved 

 any fragment of the supposed ancient continents, nor of the deposits 

 which must have resulted from their denudation. ' 



Thirdly, the author discusses the changes of climate which have 

 influenced the dispersal of organisms, and this leads him to the 

 subject of glacial epochs and their causes, to which he devotes three 

 chapters. Those readers who are anxious to arrive at the gist of the 

 work, viz. the phenomena of insular life, will perhaps regret that 

 60 much space has been devoted to this class of speculation, and 

 some might even think that with a concise summary of conclusions 

 in the text, the rest of the matter might have been relegated to an 

 appendix, or reserved for a separate work. But these subjects are 

 1 See aute, p. 75, " Oceanic Islands," by T. M. Eeade, F.G.S. 



