218 ON THE ORIGIN, MATERIALS, COMPOSITION, 



a mere arithmetical comparison which can scarcely 

 deceive. 



Every thing proves that the present secondary 

 strata are the produce of more antient rocks; and 

 these must have been the immediate successors of 

 those which are now the primary ; as we have no 

 reason to imagine that there has been a distinct series 

 which has entirely vanished. The proportions of the 

 different materials in the produce, ought therefore to 

 bear a certain relation to those in the original repo- 

 sitories ; or, if there was a difference, it would be ex- 

 pected to be in favour of the most yielding materials, 

 schist and limestone. But if we examine the quantity 

 of limestone in the primary strata, it will be found 

 very small. What the exact proportion to the other 

 rocks may be, throughout the world, is not known; 

 but, in Britain, it certainly does not amount to a ten 

 thousandth part of the whole. But among the se- 

 condary strata of England, the limestones bear a far 

 larger proportion to the siliceous and argillaceous 

 rocks. If we were to assume only the ratio of one 

 hundredth, it would answer the purposes of the pre- 

 sent argument ; and there is nothing unreasonable in 

 referring the origin of the British secondary strata to 

 the British primary rocks, with the necessary excep- 

 tions, of course, as to these calcareous strata. This 

 however is a matter of indifference; as the general 

 fact, taking the whole world, is indisputable. 



Thus it may fairly be inferred, that while the sili- 

 ceous and argillaceous secondary strata have been 

 formed from the ruins of more antient rocks, a large part 

 at least of the calcareous, is the produce of animals. 

 Hence also it must appear, that from the operations 

 of animals., the quantity of calcareous earth deposited 



