384 W. H. HOBBS 



PROBABLE EXPLANATION OF THE DIAMOND DISTRIBUTION 



The material from which the diamonds were derived must 

 clearly have been to the northward beyond the lakes, in the wil- 

 derness of Canada. A method which may result in locating this 

 material with some definiteness will be elaborated below. To 

 explain the occurrence of so large a proportion of the stones in 

 or near the outermost moraine, it is necessary to assume either 

 that at the beginning of the second great advance of the ice the 

 diamonds were embedded in a loose material easily transported, 

 and hence largely removed before the stages of retreat, or that 

 they were embedded in their matrix, which from its limited 

 extent was largely abraded and removed by the ice during its 

 initial stage. 



The first is the more reasonable assumption, by reason of the 

 wide fan of distribution of the diamonds, and the number which 

 has been found warrants the assumption that the number of stones 

 at the source of supply must have been very considerable. It is 

 likely that for every diamond that has been found there are a 

 thousand still undiscovered in the drift. 



Professor T. C. Chamberlin has, at my request, very kindly 

 given me his views on this question, and I have his permission to 

 print the following from a personal letter : 



In regard to the explanation of the occurrence of the diamonds in the 

 large moraines near the outer limit of the later invasion two explanations pre- 

 sent themselves : First, the diamonds were separated from their original 

 matrix in preglacial times by disintegration and accumulated in the bottoms of 

 the valleys in the vicinity of their origin. The first glaciations were not suf- 

 ficiently abrasive to remove the diamond-bearing gravels in the bottoms of the 

 valleys, or at least not able to do so completely. The diamonds, therefore, 

 do not occur frequently in the earlier drift material. Furthermore, the 

 earlier drift material was less subjected to wash and now appears less abun- 

 dantly as clean gravel and hence a less proportion of the diamonds that may 

 have been embraced in it have been found. The chances of finding diamonds 

 scattered throughout the till is of course relatively small. 



The second hypothesis postulates a sufficient interval between the earlier 

 glacial invasion and the later to permit the disintegration of the diamond-bear- 

 ing matrix and the freeing of the diamonds which became subject to trans- 

 portation and accumulation in the wash from the moraines of the later drift. 



