COMMENCEMENT OF ORGANIC LIFE. 33 



ry non-fossiliferous rocks to the termination of the car- 

 boniferous series, for there we see vast deports (coal) con- 

 taining carbon as a large ingredient, while at the same time 

 the leaves of the Stone Book present no record of the con- 

 temporaneous existence of land animals. 



The hypothesis of the connection of the first limestone 

 beds with the commencement of organic life upon our 

 planet is supported by the fact, that in these beds we find 

 the first remains of the bodies of animated creatures. My 

 hypothesis may indeed be unsound ; but, whether or not, 

 it is clear, taking organic remains as upon the whole a 

 faithful chronicle, that the deposition of these limestone 

 beds was coeval with the existence of the earliest, or all 

 but the earliest, living creatures upon earth. 



And what were those creatures ? It might well be with 

 a kind of awe that the uninstructed inquirer would wait 

 for an answer to this question. But nature is simpler than 

 man's wit would make her, and behold, the interrogation 

 only brings before us the unpretending forms of various 

 zoophytes and polypes, together with a few single and 

 double- valved shell- fish, (mollusks,) all of them creatures 

 of the sea. It is rather surprising to find these before any 

 vegetable forms, considering that vegetables appear to us 

 as forming the necessary first link in the chain of nutri- 

 tion ; but it is probable that there were sea plants, and 

 also some simpler forms of animal life, before this period, 

 although of too slight a substance to leave any fossil trace 

 of their existence. 



The exact point in the ascending stratified series at 

 which the first traces of organic life are to be found is not 

 clearly determined. Dr. M'Culloch states that he found 

 fossil orthocerata (a kind of shell-fish) so early as the 

 gneiss tract of Loch Eribol, in Sutherland ; but Messrs. 

 Sedgwick and Murchison, on a subsequent search, could 

 not verify the discovery. It has also been stated, that the 

 gneiss and mica tract of Bohemia contains some seams 

 of grawacke, in which are organic remains ; but British 

 geologists have not as yet attached much importance to 

 this statement. We have to look a little higher in the 

 series for indubitable traces of organic life. 



Above the gneiss and mica slate system, or group of 

 strata, is the Clay Slate and Grawacke Slate System ; 

 that is to say, it is higher in the order of supraposition, 

 though very often it rests immediately on the primitive 



