LIFE ON THE EARTH. 121 



to trace, the terms 'Azoic' and 'Hypozoic' have been 

 suggested. Thus arises the second great epoch in 

 geological chronology the epoch of Life on the Earth 

 the starting-point of Palaeontology. How shall we 

 proceed to collect evidence which may bring that 

 remote event into a scale of solar time? What na- 

 tural phenomena can be found, so much alike in all 

 past periods of time, and so related to years and 

 cycles of years, as to be safely employed in estimat- 

 ing, not only the relative antiquity of the several 

 races of plants and animals, but the absolute anti- 

 quity of the earliest inhabitants of the earth? 



The Geological Scale of Time is founded on the 

 series of the strata deposited in the ancient sea; if 

 the forces tending to produce such deposits have 

 always been productive of equal effects in equal 

 times, the thicknesses of the strata are exact mea- 

 sures of the times ; the thickness added in a certain 

 historical time to the modern sea-bed, will bear the 

 same proportion to the total thickness which has 

 been added in geological time as the historical time 

 ascertained to the geological time required. This 

 view of the uniformity of natural effects, in the 

 strict terms here assigned, is perhaps held by none 

 of the followers of Hutton, however nearly some 

 expressions of the eminent author of the Principles 

 of Geology may seem to approach it. It cannot be 



