REVIEW AND GENERAL DISCUSSION 



491 





mined in any way, through all the ridges in the country over which my work extended, between 

 the North Fork of the American and the Mokelumne River. 



There is a possibility that a channel may run through from Grizzly Flat to the Morning Star 

 mine. 



The main channel at Damascus, that is, the "Mountain Gate" channel, appears to be well defined, 

 running into the ridge in a direction nearly due southeast (magnetic). How deep this channel 

 may be cut in the bed-rock, and how wide it may be across its top from rim to rim, is very un- 

 certain. But from such indications as can be seen along the sides of the hills, it seems likely that 

 its breadth is considerable, and that the maximum height of its rims above its bed may reach, in 

 places at least, from 200 to 300 feet. The barometric observations show that the bed of this 

 channel passes through the present hill at a depth of not less than about 800 feet beneath its 

 crest ; of which depth the whole mass, with the exception of the comparatively thin layer of 



gravel which fills the bottom of the channel, appears to consist of volcanic conglomerates and 

 breccias. 



The accompanying notes will show how far this channel has already been followed in the 

 tunnels. But how much farther it may continue to hold its southeasterly course, and where it 

 ultimately goes to, are points which remain to be proved, and upon which there are many different 

 opinions among the miners. 



The main ridge beneath which it passes in the vicinity of the Forks House is two or three 

 miles wide, and there are several possibilities in the case. But I shall add a few remarks on 

 this point further on. 



Where this channel came from towards the northwest has also been a much-vexed question. 

 The character of its gravel is peculiar, it being by far the purest quartz gravel winch I have seen 

 in the country, and containing the most numerous and the largest white quartz boulders, among 

 which masses of forty to fifty tons in weight are not uncommon. The grade of this channel is not 

 uncommonly heavy, and I do not think such enormous boulders can have travelled very far 

 along its bed. 



I can only explain their presence here, in connection with a gravel of which the sand as well as 

 the smaller pebbles consist almost exclusively of quartz, by supposing that somewhere alono- the 

 course of the ancient stream, at no great distance from their present resting-place, there once existed 

 an enormous mass of quartz in the region which has since been excavated to form the tremendous 

 canons of the branches of the North Fork of the American ; and that, while this quartz was broken 

 up to form the present gravel, the slates and other rocks which were associated with it being 

 softer, and liable also to disintegration by chemical means, were entirely ground to sand and silt 

 and completely washed away. 



I am told no indications of the existence of such a channel as this have ever been found either 

 on the opposite side of the North Fork of the river or higher in the mountains among its branches 

 to the northeast. But since, in the near vicinity of Damascus, the North Fork of the American 

 River splits up into three or four large branches, and the canons here are very deep and the ridges 

 narrow for some distance above the forks, there is a considerable area here in which the ridges and 

 spurs, though very precipitous, do not rise high enough to touch the plane of the ante-volcanic 

 gravel, and any vestiges of ancient channels which may have once existed within this area have 

 since been swept away. Under such circumstances, I think the most probable solution of the 

 question, Whence came the Damascus channel? is the supposition that, if we could have fol- 

 lowed up its ancient course for a short distance farther to the northwest over the region now occu- 

 pied by the basin of the Humbug Canon and the branches of the river, we should have found it 

 then to curve gradually around to the north and northeast and probably to split up into various 

 smaller channels, and thus to completely lose both its size and its distinctive character long before 

 it would reach any of the present ridges in the higher northeastern country at points where any 

 remnants of these branches might now be traced. 



It will be noticed as an exceptional fact that at Canada Hill there seems to have existed a well- 



