70 [APPENDIX 



turbed position is not the only change observable in these cases ; struc 

 tural change is as often the result of the intrusion among the slates as the 

 appearance of the veins themselves. The above peculiarities in relation 

 to these views are observable in every part of the lower mining districts, 

 and an erroneous opinion in regard to the age of the dike' under exami 

 nation may easily occur as the part urider our observation may be situated 

 either in the primitive or sedimentary rocks. 



A dike of this character occurs in the town of Centreville, Placer 

 County, and extends in a northerly direction for one and a half miles 

 through granite, when it enters the slates, passing entirely through their 

 length and again appearing in granite at their northern extremity ; an 

 other instance of a similar character is met with on Deer Creek, two 

 miles below Nevada ; here the dike passes through the trap, granite and 

 slate, and also at Newtown in the same county. Still further north, in 

 the County of Yuba, a vein cuts both the granite and slate, as in the 

 vicinity of Brown's Valley,' and again on Dry Creek ; in many other 

 localities throughout this range of country, the same features are to be 

 found, and our opinion on the comparative ages of these veins, can be 

 correctly founded only by a careful examination of the entire length of . 

 the vein. 



On the same range of hills, this group is continued south as far as 

 the Tuolumne River, and includes the district on which some of the 

 principal companies of the southern counties are located. It frequently 

 happens that the veins of' this group are composed, of a perfect net-work 

 of small threads and veins, varying in power from one inch to one foot. 

 This peculiarity is admirably exemplified at Angel's Camp in Calaveras 

 County, at this locality and for miles around these small "hilos" con 

 stitute a large part, of tiie rich veins of this section, while at the distance 

 of four miles to the south, it again appears as a . mammoth dike, popu 

 larly known as the "Great Carson Hill Vein," which extends southerly 

 to the Stanislaus River. 



From this point a line of large dikes interrupted at inte^rvals continue 

 in a southeast direction for sixty miles, passing through Campo Seco, 

 Coulteryille, Bear Valley, and thence to Mi Ophir; throughout this 

 entire distance they are found to cut through all other volcanic rocks, 

 with perhaps one or two exceptions ; the lasaltic rocks in some parts of 

 the southern counties bear evidence of displacement by these intrusions, 

 and I know of but two cases in which the latter intrusions have thrown 

 these veins, and in these cases it is not yet fully determined whether 

 this be the fact. It is on the west flanks of the hills in. which the dikes 

 of the recent group of quartz appears, that the features which mark 

 their age are more particularly noticeable ; here the slates (and in the 

 foothills, the sandstone) present all the varied changes of position and 

 structure, noticed by different writers on the physical features incident 

 to the mountain districts of California at one time dipping east at an 

 other west, and again half inverted, in the multifarious disturbances to 

 which they have been subjected. 



The greatest amount of displacement in the sedimentary rocks is 

 always found in the closest proximity to the veins in their immediate 

 vicinity, and although a e*tical position only may be given in many 

 instances, yet this is found to become less as you recede from the vein 



