328 ILLOGICAL GEOLOGY. 



fossils of our caiboniferous rocks and those of the marine 

 strata deposited at the same period. But though, in tha 

 abstract, the danger of basing positive conclusions on evi- 

 dence derived from fossils, is clearly recognized ; yet, in the 

 concrete, this danger is generally disregarded. The estab- 

 lished conclusions respecting the ages of strata, take but 

 little note of it ; and by some geologists it seems altogether 

 ignored. Throughout his Siluria^ Sir R. Murchison habit- 

 ually assumes that the same, or kindred, species, lived in 

 all parts of the Earth at the same time. In Russia, in Bo- 

 hemia, in the United States, in South America, strata are 

 classed as belonging to this or that part of the Silurian sys- 

 tem, because of the similar fossils contained in them — are 

 concluded to be everywhere contemporaneous if they en- 

 close a proportion of identical or allied forms. In Russia 

 the relative position of a stratum is inferred from the fact 

 that, along with some Wenlock forms, it yields the JPenta- 

 ineru8 ohlongus. Certain crustaceans called Eurypteri, be- 

 ing characteristic of the Upper Ludlow rock, it is remarked 

 that " large Eurypteri occur in a so-called black grey-wacke 

 slate in Westmoreland, in Oneida County, New York, 

 which will probably be found to be on the parallel of the 

 Upper Ludlow rock : " in which word " probably," we see 

 both how dominant is this belief of universal distribution 

 of similar creatures at the same period, and how apt this 

 belief is to make its own proof, by raising the expectation 

 that the ages are identical when the forms are alike. Be- 

 sides thus interpreting the formations of Russia, England, 

 and America, Sir R. Murchison thus interprets those of the 

 antipodes. Fossils from Victoria Colony, he agrees with 

 the Government-surveyor in classing as of Lower Silurian 

 or Llandovery age : that is, he takes for granted that when 

 certain crustaceans and moUusks were Uving in "Wales, cer- 

 tain similar crustaceans and mollusks were living in Aus- 

 tralia 



