to Section C {Geology). 



453 



when brought into contact with silicates like those which formed 

 the primitive crust. As a result of its action saline solutions and 

 chemical deposits would be formed; the latter, however, would 

 probably be of no great thickness, for the time occupied by the 

 ocean in cooling to a temperature not far removed from the present 

 would probably be included within a few hundreds of years. 



The Stratified Series. 



The course of events now becomes somewhat obscure, but sooner 

 or later the familiar processes of denudation and deposition started 

 into activity, and have continued acting uninterruptedly ever since. 

 The total maximum thickness of the sedimentary deposits, so far as 

 I can discover, appears to amount to no less than 50 miles, made up 

 as follows : — 



Geologists, impressed with the tardy pace at which sediments 

 appear to be accumulating at the present day, could not contemplate 

 this colossal pile of strata without feeling that it spoke of an almost 

 inconceivably long lapse of time. They were led to compare its 

 duration with the distances which intervene between the heavenly 

 bodies ; but while some chose the distance of the nearest fixed star 

 as their unit, others were content to measure the years in terras of 

 miles from the sun. 



Evolution of Organisms. 



The stratified rocks were eloquent of time, and not to the geologist 

 alone, they appealed with equal force to the biologist. Accepting 

 Darwin's exjjlanation of the origin of species, the present rate at 

 which form flows to form seemed so slow as almost to amount to 

 immutability. How vast, then, must have been the period during 

 which by slow degrees and innumerable stages the protozoon was 

 transformed into the man 1 And if we turn to the stratified column 

 what do we find ? Man, it is true, at the summit, the oldest fossili- 

 ferous rocks 34 miles lower down, and the fossils they contain 

 already representing most of the great classes of the Invertebrata, 

 including Crustacea and Worms. Thus the evolution of the Verte- 

 ■brata alone is known to have occupied a period represented by 



