Doc. No. 9.] 69 



characteristics they present, so far as relates to their mineral constituents, 

 but there is one remarkable feature attending them here (as also to the 

 north in a few instances,) which is not common to the granitic associa 

 tions of these rocks, viz : the depth to which the vein is decomposed from 

 the surface down, will not exceed more than one-fourth that which will 

 be found where the inverting rock. is of the granitic series. This pecu 

 liar feature is very striking in passing from a " sett " situated in the latter 

 to one located in the former, and will be found to hold good even in the 

 same neighborhood. 



One other feature is equally apparent, and at the same time important 

 in connection with this, which is, that while those veins present the con 

 trast above noted, the "setts" occuring in the serpentive series which 

 have been unaffected by the cause producing such extensive decomposi 

 tion as is found among the granite rocks, do not possess a texture so firm 

 and coherent as the veins found in the northern sections, such veins will 

 be worked with a less amount of labor and capital producing an equal 

 amount of ore. 



There is nothing to distingu^s^ the veins of this section from being of 

 the same age with those at the north, and running through a similar range 

 of country, like the veing of the granitic series they do not appear to 

 have disturbed the more recent formation of the tertiaries, but are con 

 fined exclusively to the primitive rocks. Following a line west toward 

 the valleys, the occurrence of a more recent group becomes manifest, and 

 is unquestionably the equivalent of that alluded to as occurring through 

 out the northern counties. 



RECENT GEOUP. , 



This group of these rocks is found extending from the lowest foot-hills 

 on the east border of the valley r where the first outcrop of the slates are 

 met, to a distance of about eighteen miles to the east, and after is found 

 running into tfee western edge of the older group ; their intrusion ap 

 pears to have formed one of the principal and later disturbing agents 

 that has been in action in those periods of development of that part of 

 this country, immediately preceding, and continuing into the middle 

 Eocene and Miocene periods of the tertiary era. 



Their altitude above the sea is variable, from one hundred to fifteen 

 hundred feet, and some few localities reach the height of two thousand. 

 One of the features, which this group presents, and which distinguishes 

 it from those of the older group is, that they have cut through and dis 

 turbed not only the primitive formations, but every other formation 

 found resting upon them, this occurs in almost every case in which these 

 rocks are found. A dike of this age is often found protruding through 

 the granite or some other member of the primitive series, and may be 

 traced frequently for one or two miles before any member of the sedi- 

 mentry rocks are met with ; in this case, the latter rocks will be found 

 more or less disturbed at the point of contact with the vein, and it will 

 often be found that its passage from the granite beneath into the slates 

 above is perfect, traversing the overlying rocl^ through a great part of 

 its length, and sending out cross courses in every direction. A di-s 



