Silurian Focks. 83 



sand, they afford positive proof of the pre-existence of land 

 and water, and atmospheric destructive agency to supply the 

 materials of these strata, and the bed of a sea to receive them. 

 Is it not highly improbable that this sea was untenanted \ 

 There must doubtless be a lowest sedimentary stratum, the 

 materials of which must have been derived from land com- 

 posed of non-sedimentry rocks. By "non-sedimentary" I 

 mean a rock, the formation of which may, with the greatest 

 probability, be ascribed to igneous action. Whether it was 

 granite, or any other form of igneous rock with which we are 

 acquainted, we cannot tell ; because of the great uncertainty 

 as to how far the lowest sedimentary deposits have under- 

 gone changes by metamorphic action ; but that silica and clay 

 and very little lime entered into its composition is evident 

 from the predominance of the two former earths in all the 

 oldest strata, and the comparative rarity of lime. 



But animal and vegetable life may have existed while the 

 land that afforded the materials for the first sedimentary de- 

 posits was wholly composed of un stratified rocks. Nor is it 

 necessary to have recourse to the obliteration by metamor- 

 phic action in all cases where there are no traces of organic 

 remains. We have learned from the valuable report by Pro- 

 fessor Edward Forbes of his researches in the -^gean Sea, 

 that there are profound depths in which no animals and no 

 vegetables seem capable of living ; and thus, as there may 

 be now, and probably are, deposits of vast thickness produced 

 without organic bodies having ever lived in or upon them, in 

 the profound depths of the Atlantic and Pacific Oceans, so is 

 the absence of such remains in any stratum no proof, that 

 when it was deposited there might not have existed above it 

 a sea teeming with life. I cannot support this view better 

 than by quoting what Professor Forbes says on the subject : 

 " As in the sea there is a zero of vegetable life, so, we may 

 fairly infer, is there one of animal life. All deposits formed 

 below that zero will be void, or almost void, of organic con- 

 tents. The greater part of the sea is far deeper than the 

 point zero ; consequently the greater part of deposits form- 

 ing will be void of organic remains. Hence we have no right 

 to infer that any sedimentary formation, in which we find few 



