THE EOZOIC AGES. 20 



residual carbon, there must have been abundance of 

 organic matter, either growing at the bottom, or 

 falling upon it from the surface ; and as the Eozoon 

 limestones are usually free from such material, we may 

 assume that the animal life in them was sufficient to 

 consume the vegetable pabulum. On the other hand, 

 as detaclied specimens of Eozoon occur in graphitic 

 limestones, wo suppose that in some cases the vege- 

 table matter was in excess of the animal, and this may 

 have been either because of its too great exuberance, 

 or because the water was locally too shallow to permit 

 Eozoon and similar creatures to flourish. These 

 details we must for the present fill up conjecturally ; 

 but the progress of discovery may give us further 

 light as to the precise conditions of the beginning of 

 life in the ''great and wide sea wherein are moving 

 things innumerable,^^ and which is as much a wonder 

 now as in the days of the author of the " Hymn of 

 Creation,^^* in regard to the life that swarms in all 

 its breadth and depth, the vast variety of that life, 

 and its low and simple types, of which we can affirm 

 little else than that they move. 



The enormous accumulations of sediment on the 

 still thin crust of the earth in the Laurentian period 

 — accumulations probably arranged in lines parallel 

 to the directions of disturbance already indicated — 

 weighed down the surface, and caused great masses 

 of the sediment to come within the influence of the 

 heated interior nucleus. Thus, extensive meta- 

 • Psalm civ. 



