R^SUM^, AND GENERAL DISCUSSION. 543 



is, that it seems as if the idea that a high temperature had been one of 

 the factors iu tlie mysterious operation of making the diamond had 

 received a certain additional amount of corroborative evidence in conse- 

 quence of the association of that gem with volcanic materials in the 

 most productive diamantiferous district the world has ever known. 



That the conditions under which this precious gem has been formed 

 arc very exceptionaj, can be safely inferred from the extremely small 

 amount of the material which has been originated. Not that the dia- 

 mond is limited, or almost exclusively so, to one locality, like certain 

 minerals, — as, for instance, cryolite and red oxide of zinc. It occurs, 

 on the contrary, all over the world, but never — so far as yet observed 

 — in masses weighing more than a few hundred grains; while, if all the 

 specimens of this gem which go to help make up the crown-jewels of all 

 the empires and kingdoms of the world were put together, their united 

 weight would certainly not exceed a few pounds.* 



The inference from that which has been stated above is, that we are 

 not justified in assuming that the occurrence of graphite in the azoic 

 rocks is a proof that this material has resulted from the action of or- 

 ganic agencies, or, in other words, that life existed on the globe at the 

 time these rocks were deposited. The fact that no recognizable traces 

 of such life have ever been found in connection with the graphite of the 

 Azoic series, is "decidedly an important item in this connection ; and we 

 consider that geologists are not justified in assuming the presence of life 

 when they not only have no positive evidence of its existence, but when 

 the theoretical probabilities are strongly in opposition to this view. 



The idea that the presence of carbonate of lime must necessarily be 

 taken as a proof of the former existence of life — as is so positively 

 asserted by Bischof, Dana, and many other geologists — seems to us 

 entirely at variance with the facts. It is impossible for any one famil- 

 iar with the mineralogical occurrence of carbonate of lime to deny that 

 the formation of this material is a process which is going on, in innu- 

 merable localities and on a grand scale, without the intervention of 

 organized existences. 



Every metalliferous vein is likely to have, and in many instances 

 such veins do have, the metallic sulphides which they contain — sul- 

 phur being by far the most common mineralizer of the metals — more 

 or less completely converted into carbonates at their outcrops. Thus, 

 ■while chalcopyrite is the most common ore of copper, the carbonate of 



* The total weight in iJie rour/h of thirteen of the largest and most celebrated dia- 

 monds in the world was only a little over a poimd. 



