292 GEOLOGICAL SUEVEY OF THE TEERITOEIES. 



be said about theii\ It is evident that if all the finely-disseminated 

 metalliferous minerals could be collected at a moderate expense, and 

 their valuable constituents extracted, a considerable saving would be 

 effected in the expenses of mining. To this end it becomes necessary to 

 concentrate the ores, to separate, by such means as may be found most 

 effective and cheapest, the dead rock from the valuable minerals that 

 are contained in it. Although but small beginnings have been made in 

 that direction, it is to be hoped that they will succeed, and raise the 

 productions of the mines by the more economical treatment of ores. In 

 Europe, concentration of ores has become a ma^£ter of vital importance, 

 and in our western country it would greatly assist mining enterprise, 

 although it is not yet so imperatively demanded. 



Mining is carried on economically, as a rule, in this as well as in the 

 other districts of Colorado. Ordinarily a shaft is sunk down on the vein, 

 which is a matter of little difficulty remembering the surprising regu- 

 larity of the dips. From this shaft, which usually follows the dip, 

 levels are struck off into either side of the vein, sometimes certain dis- 

 tances apart, sometimes at random, or according to the prospects of 

 finding a large body of ore. These levels are driven either to the limits 

 of the claim or their termination is induced by a deterioration of the ore, 

 or an irregularity of the vein that may be destructive to the ore- body. 

 By means of overhand and underhand stoping, the ore is taken out, and 

 conveyed either on a tramway or by hand to the shaft, and thence hoisted 

 Tip by steam-power, horse-power, or by a hand-windlass. Should the 

 mine be more extensive, other shafts are sunk, as necessity may require 

 it ; vertical connections between the different levels are made, partly to 

 facilitate the extraction of ore, partly to regulate the supply of fresh air ; 

 and apparatus for controlling the collecting waters are constructed. 

 Mr. Hague, in his report on the mining industry of Colorado, has dwelt 

 considerably upon these points, and to his book I would refer any one 

 seeking information with regard thereto. 



In illustration of the above remarks, a diagram representing the work 

 done in the Monte Cristo mine is given on Plate Y. The dark shades 

 indicate how much of the ore has been taken out. 



A continuation of this process of extracting the ore throughout the 

 entire vein from the surface downward seems to have one disadvantage, 

 however. I am fully aware that a method of this kind is demanded by 

 the very simple fact that the men owning and working the greater por- 

 tion of the mines are not men of capital, and it is necessary that they 

 should derive from their mines as much remuneration as possible at the 

 smallest expense. Therefore, they rob the vein of all its contents so far 

 as of any use to them directly from the surface downward, frequently 

 along the entire extent of their claim, leaving a long, narrow aperture in 

 the hill, on which they may be working, of sometimes 100 feet in depth. 

 It is evident that in course of time progressing decomposition of the 

 rock exposed to atmospheric influences, among which the accumulation 

 of snow in the crevice thus formed is one of the strongest, combined 

 with the more or less direct pressure which is experienced by the rocks 

 on either side of this fissure, will result in rendering the walls very un- 

 safe — so much, so, perhaps, that great expense must be incurred here- 

 after if operations are pushed farther downward in the same mines. 



As stated above, Mr. Briggs has kindly furnished me with some data 

 regarding price of labor, conditions of contracts, &c. This was in May 

 and June, 1873. The wages of a miner per day are $3 to $3.50 for work 

 in the mine, lasting ten hours during the day, nine during night. Brake- 

 men receive $3.50 for twelve hours' work. When leasing a mine, the 



