124 LIFE ON THE EAKTH. 



temperature of the surface of the globe; with this 

 decrease the disturbances from the interior are sup- 

 posed to diminish, and the action of the atmosphere 

 to be more and more approaching to a uniform rate. 

 I propose to consider the computations which may 

 be founded on these different views. 



Nothing can be simpler in aspect than the pro- 

 blem of the age of the stratified crust of the globe 

 on the Uniformitarian hypothesis. We have only 

 to find out the rate of accumulation of sediment in 

 the sea the thickness of deposits produced in a 

 year, or century, or some long historic period and 

 apply this measure or rate to the ancient deposits. 

 This modern rate of progress of deposits is very un- 

 equal ; great along some shores, which thus are 

 stretching outwardly to contract the domain of the 

 sea, insensible on others, especially where sea-cur- 

 rents sweep the coast and carry away the sediments to 

 other situations. But so it was in ancient times, for 

 none of our strata have more than a limited range, 

 and some of those that are most extensive may be 

 reasonably thought to have acquired their large 

 breadths by oceanic currents which disturbed and 

 redistributed sediments over areas greater than those 

 of original deposition. 



The distance to which fine sediments brought by 

 rivers are carried in the ocean is found much to ex- 



