270 CONTEMPORANEITY OP STRATA AND THE 



poraneous" in the strict sense of this term. On the contrary, in so 

 far as we can judge from the known facts of the present distribution 

 of living beings, the recurrence of exactly the same fossils in beds far 

 removed from one another is prima facie evidence that the strata 

 are not exactly contemporaneous ; but that they succeeded one 

 another in point of time, though by no long interval geologically 

 speaking. 



Most of the facts bearing upon this question may be elicited by a 

 consideration of such a widely extended and well-known formation 

 as the Mountain Limestone or Sub-carboniferous Limestone. This 

 formation occurs in localities as remote from one another as Europe, 

 Central Asia, North America, South America, and Australia ; and it 

 is characterised by an assemblage of well-marked fossils, amongst 

 which Brachiopods belonging to the genus Producta may be specially 

 sino-led out. Now, if we believe that the Carboniferous Limestone 

 in all these widely distant localities was strictly contemporaneous, 

 we should be compelled to admit the existence of an ocean embraciag 

 all these points, and, in spite of its enormous extent, so uniform in 

 temperature, depth, and the other conditions of mariae life, that 

 beings, either the same or very nearly the same, inhabited it from 

 end to end. "We can, however, point to no such uniformity of 

 conditions and consequent uniformity of life over any such area at 

 the present day; and we have, therefore, no right to assume that this 

 is the true explanation of the facts. Indeed, this explanation would 

 almost necessarily lead us to the now abandoned theory, that each 

 period in geological history was characterised by a special group of 

 organisms spreading over the whole globe, and that there took place 

 at the close of each period a general destruction of all existing forms 

 of life, and a fresh creation of the new forms characteristic of the 

 next period. 



In our inability, then, to accept this view, we must seek for some 

 other explanation of the observed facts. The most probable view, 

 and the one which is supported most strongly, both by what we see 

 at the present day, and by what we learn from numerous examples in 

 past time, is this : — The Carboniferous Limestone was not deposited 

 all over the world in one given period, by one sea, or at exactly 

 the same time ; so that it can not be said to be strictly " contem- 

 poraneous" wherever it is found. This would imply a uniformity of 



