THE KLONDIKE GOLD DISTRICT. 289 



great mass of rock would account for all tho gold which was left 

 behind in the present surface deposits. 



The placer gold found within the limits of each different class of 

 original rock in the district is known to be sufficiently different in 

 fineness and other characters to enable the assayers to recognise its 

 source with certainty, and this is regarded as one of the proofs that 

 the gold has merely sunk down, as it was liberated, within the original 

 area of its matrix, while the lighter materials were being washed 

 away, and that it has suffered but little horizontal movement. 



The White Channel and Klondike Gravels. 



The White Channel and the associated Klondike gravels are the 

 oldest detrital deposits of the district, having been formed, as already 

 described, by the first washing of the sea as the deeply decayed Mid- 

 Tertiary land surface sank gradually beneath its waters, exposing 

 every part in turn to its action. This is believed to have taken place 

 in Pliocene times. Portions of these gravels having remained where 

 they had been originally deposited, others, which have been subse- 

 quently formed at various periods, present a variety of relations 

 to the older ones, which still remain the greatest in quantity. Some- 

 times the ancient gravels occur side by si^e with the newer ones 

 in the valley bottoms, and both are profitably mined. On Hunker 

 and Bonanza Creeks the volume of the white gravel increases in 

 width and depth in proceeding down stream, showing a continuation 

 of the conditions that accumulated this gravel, while the land sank 

 and rose again. A considerable amount of gold has been concentrated 

 under the gravel. 



Great Interval Follows. 



It has been already shown that since the close of the White 

 Channel period, sufficient time has elapsed for the excavation of creek 

 valleys to depths of 300 to 600 ft., through what was originally hard 

 schist rock. This long period would permit of many geological 

 changes taking place, some of which may have afPected the aiTange- 

 ment of the auriferous deposits or caused a redistribution of the gold, 

 and we must take this possibility into consideration in attempting to 

 account for the present modes of occurrence of the precious metal. 

 Therefore, the reason why some portions of the Klondike district are 

 richer than others, and that certain peculiarities occur in the relative 

 abundance of the gold in different parts, may not be entirely attri- 

 butable to differences in the original productiveness of the rocks of 

 tho various localities, but may be due, in part, to this redistribution 

 of the old auriferous gravels. 



Remains of Mammals and Trees in Frozen Ground. 



The Klondike district has experienced two long periods of rock 

 decay — one before and one after the submergence in Tertiary times, 

 already referred to. Towards the close of the latter period the dis- 

 integrated stony debris and accompanying earth, silt, &c., became 

 deeply frozen at a time which probably corresponds to the latest 



