GEOLOGICAL CONTEMPORANEITY ix 



wishes to prove an alibi, it is of no use for him to 

 get a thousand witnesses simply to swear that 

 they did not see him in such and such a place, 

 unless the witnesses are prepared to prove that 

 they must have seen him had he been there. But 

 the evidence that animal life commenced with the 

 Lingula-flags, e.g., would seem to be exactly of this 

 unsatisfactory uncorroborated sort. The Cambrian 

 witnesses simply swear they " haven't seen any- 

 body their way " ; upon which the counsel for the 

 other side immediately puts in ten or twelve 

 thousand feet of Devonian sandstones to make 

 oath they never saw a fish or a mollusk, though 

 all the world knows there were plenty an their 

 time. 



But then it is urged that, though the Devonian 

 rocks in one part of the world exhibit no fossils, 

 in another they do, while the lower Cambrian 

 rocks nowhere exhibit fossils, and hence no living 

 being could have existed in their epoch. 



To this there are two replies : the first that the 

 observational basis of the assertion that the lowest 

 rocks are nowhere fossiliferous is an amazingly 

 small one, seeing how very small an area, in com- 

 parison to that of the whole world, has yet been 

 fully searched ; the second, that the argument is 

 good for nothing unless the unfossiliferous rocks 

 in question were not only contemporaneous in the 

 geological sense, but synchronous in the chronolo- 

 gical sense. To use the alibi illustration again. 



