254 THE POORNESS OF OUR [CHAP. X. 



their accumulation, are entirely destitute of organic remains, 

 without our being able to assign any reason: one of the most 

 striking instances is that of the Flysch formation, which consists 

 of shale and sandstone, several thousand, occasionally even six 

 thousand feet in thickness, and extending for at least 300 miles 

 from Vienna to Switzerland ; and although this great mass has 

 been most carefully searched, no fossils, except a few vegetable 

 remains, have been found. 



With respect to the terrestrial productions which lived during 

 the Secondary and Palaeozoic periods, it is superfluous to state 

 that our evidence is fragmentary in an extreme degree. For 

 instance, until recently not a land-shell was known belonging to 

 either of these vast periods, with the exception of one species 

 discovered by Sir C. Lyell and Dr. Dawson in the carboniferous 

 strata of North America ; but now land-shells have been found 

 in. the lias. In regard to mammiferous remains, a glance at the 

 historical table published in Lyell's Manual will bring home the 

 truth, how accidental and rare is their preservation, far better 

 than pages of detail. Nor is their rarity surprising, when we 

 remember how large a proportion of the bones of tertiary 

 mammals have been discovered either in caves or in lacustrine 

 deposits ; and that not a cave or true lacustrine bed is known 

 belonging to the age of our secondary or palaeozoic formations. 



But the imperfection in the geological record largely results 

 from another and more important cause than any of the fore- 

 going ; namely, from the several formations being separated from 

 each other by wide intervals of time. This doctrine has been 

 emphatically admitted by many geologists and palaeontologists, 

 who, like E. Forbes, entirely disbelieve in the change of species. 

 When we see the formations tabulated in written works, or when 

 we follow them in nature, it is difficult to avoid believing that 

 they are closely consecutive. But we know, for instance, from 

 Sir E. Murchison's great work on Russia, what wide gaps there 

 are in that country between the superimposed formations ; so it 

 is in North America, and in many other parts of the world. The 

 most skilful geologist, if his attention had been confined ex- 

 clusively to these large territories, would never have suspected 

 that, during the periods which were blank and barren in his own 

 country, great piles of sediment, charged with new and peculiar 

 forms of life, had elsewhere been accumulated. And if, in each 

 separate territory, hardly any idea can be formed of the length 

 of time which has elapsed between the consecutive formations, 

 we may infer that this could nowhere be ascertained. The 

 frequent and great changes in the mineralogical composition of 

 consecutive formations, generally implying great changes in the 

 geography of the surrounding lands, whence the sediment was 



