igoi] Chalmers — Gold-Bearing Alluvions. 35 



had underg-one transportation and modification by the action of 

 rivers and streams. Prolonged shifting" of the gravels and their 

 gold content in this manner, assorting and reasserting the materi- 

 als and the sifting out of the least weighty, allowing the gold and 

 other heavy particles to settle to the bottom — were the processes 

 which brought about the conditions which we now find existing as 

 regards these auriferous deposits. 



In the glacial period which followed, these river beds were 

 buried beneath sheets of boulder-clay. The thickness of the boul- 

 der-clay in the Chaudiere valley is 100 feet or more. The ancient 

 valley of the Gilbert was likewise filled with it to a depth of 25 to 

 50 feet. 



On the withdrawal of the ice of the glacial period the rivers 

 began to clear out their ancient channels cutting down into the 

 boulder-clay and other beds, and in many places eroding the g^old- 

 bearing gravels beneath, and once more exposing them to view. 

 But in some valleys, as for example in that of the Gilbert, the 

 river was diverted from its original channel and caused to form a 

 new one, and the auriferous gravels in the pre-glacial channel have 

 thus been preserved from erosion. In these valleys the ancient 

 channel is generally at a lower level. The pre-glacial channel of 

 the Gilbert is from 30 to 85 feet below the bed of the present river 

 in that part wrought for gold, and from 100 to 400 feet or more to 

 the south of it. All the river valleys have, however, undergone 

 dislocations during and since the glacial period, so that while some 

 parts of a pre-glacial river channel may be considerably lower than 

 the present one, in other places it is not. 



From all the facts which have been obtained it would seem 

 that the alluvial gold is entirely of local origin, that is, the gravels 

 and the gold they contain belong to the rocks of the particular 

 valley in which we now find them. But just from what rocks the 

 gold came, whether from the pre-Cambrian or Cambrian or both 

 is by no means evident. There is no question but that it is de- 

 rived from some of the quartz veins in the vicinity of where it now 

 occurs ; but as little or no quartz mining has been carried on, no 

 new tacts were obtained by us which would elucidate the problem. 

 Logan and Hunt regarded the gold as belong-ing to the oldest 

 rocks of the region, that is to the crystalline schists of the Notre 



