Doc. No. 9.] 75 



but the reverse is true, that every sett has increased in power the deeper they 

 descend. Of six companies now in successful operation in Grass Valley, 

 all of them are obtaining their ores from the greenstone, in larger quan- 

 tiry and better quality than was found to be the average in the granite 

 above : on Deer Creek it is the same, and but two mines in this district 

 still continue in the granite, viz : the Illinois and Gold Tunnel mines, 

 the lower gallery of the latter is within nine feet of the greenstone, with 

 an increasing power in the " sett" at the point of working. In the coun 

 ties of Butte and Shasta, the same fact prevails, and in each of those 

 mines, which have entered the trap there has been no diminution in the 

 power of the vein or qualities of the ore. 



The depth to which some of these veins are found to enter the green 

 stone has been fifty -five feet, at the present time, and at this depth into 

 this rock they bear all the reasonable evidence of continuing to an un 

 limited depth, and being of more recent date than their investing series. 

 The greenstone in close proximity to the dikes is found much shattered 

 and disturbed, exhibiting evidences of displacement subsequent to frac 

 ture, the inclination of the disturbed masses corresponding to the dip of 

 the vein, the line of fracture form angles of fifty to, seventy degrees to the 

 dip of the " sett," and as high as forty in some cases with the horizon ; this 

 gives a stratified appearance to these rocks ; this peculiar feature is ob- 

 serable at the Osborn Hill Mine, and is indicated by the heavy lines in 

 the sketch of its transverse section. At this mine may also be observed 

 the other peculiarities before noticed, the highly decomposed and broken, 

 character of the upper part of the greenstone of seventeen feet below ; 

 at the Lafayette and Helvetia Mine, similar features are to be observed 

 of the semi-stratified appearance of the greenstone, caused by the intru 

 sion of the quartz dike through it ; the entire length of the adit level 

 of this mine is driven entirely through this rock a distance of about 

 eleven hundred feet. 



On Deer Creek, 'five miles north of Green Yalley, we find a material 

 change in the relative position of the metallic veins to the investing rocks, 

 at the Gold Tunnel, as before remarked, the "sett" is exclusively in 

 granite, while at the Wyoming Mine, one and a half miles below, the 

 4 'sett" is situated in the greenstone inferiorly and the slate above, while 

 in the adjacent mine above the Wyoming, slate and granite in the middle 

 and greenstone below is the order of arrangement. At this mine may 

 be observed one of those interesting features noticed in the concluding 

 paragraphs of the Recent Group, and when we compare the accompany 

 ing sketches of the Osborn Hill and Wyoming, a sufficient illustration 

 of the relative ages of the group will appear. The present working 

 "sett" of the latter mine is protruded through the primitive rocks, and 

 also through the slate above them, and from its dip it must pass through 

 older veins at a depth probably not exceeding four hundred feet below 

 their present level. The slate which lies superior in this mine is evidently 

 of the same age as that occurring among the foot-hills toward the valley, 

 and as the sketch of this mine illustrates, the vein passes entirely through 

 them ; the dip of this vein is forty-three degrees east, while those of the 

 adjacent mine above varies from thirty -two to thirty-e ; ght degrees. It 

 is not surprising that a recent "sett" in passing thro ugh the cross-course 

 of an older vein, or through a part of a primitive vein, should "produce 



