TIME AND LIFE* 

 MR. DARWIN'S " ORIGIN OF SPECIES " 



EVERYONE knows that that superficial film of the earth's 

 substance, hardly ten miles thick, which is accessible to 

 human investigation, is composed for the most part of 

 beds or strata of stone, the consolidated muds and sands 

 of former seas and lakes, which have been deposited one 

 upon the other, and hence are the older the deeper they 

 lie. These multitudinous strata present such resem- 

 blances and differences among themselves that they are 

 capable of classification into groups or formations, and 

 these formations again are brigaded together into still 

 larger assemblages, called by the older geologists, primary, 

 secondary, and tertiary ; by the moderns, palaeozoic, 

 mesozoic, and cainozoic : the basis of the former nomen- 

 clature being the relative age of the groups of strata ; 

 that of the latter, the kinds of living forms contained in 

 them. 



Though but a film if compared with the total diameter 

 of our planet, the total series of formations is vast indeed 

 when measured by any human standard, and, as all action 

 implies time, so are we compelled to regard these mineral 

 masses as a measure of the time which has elapsed during 

 their accumulation. The amount of the time which they 

 represent is, of course, in the inverse proportion of the 

 intensity of the forces which have been in operation. If, 

 in the ancient world, mud and sand accumulated on sea- 

 bottoms at tenfold their present rate, it is clear that a 

 bed of mud or sand ten feet thick would have been formed 

 then in the same time as a stratum of similar materials 

 one foot thick would be formed now, and vice versd. 



At the outset of his studies, therefore, the physical 

 geologist had to choose between two hypotheses ; either, 

 throughout the ages which are represented by the accu- 

 mulated strata, and which we may call geologic time, the 



* Macmillan's Magazine, December 1859. 

 131 



