222 IRVING. 



has stated: "The apex of Terry Peak consists of basic 

 quartz-porphyry, and large deposits of talus of the same na- 

 ture are distributed on its various slopes with a few outcrops 

 of rock in place to the northwestward. Intrusive sheets of the 

 same rock occur, as shown in the following section of the 

 Snowstorm mine shaft, in Nevada gulch, about thirty- four 

 hundred feet northerly from the apex of Terry, and about mid- 

 way between that point and the apex of Green mountain. 



(i) Porphyry, 124 feet. 



(2) Shale, 10 " 



(3) Porphyry? 85 " 



(4) Shale, 30 " 



(5) Porphyry, 4.5 " 



(6) Shale, 87 " 



(7) Porphyry, 0.5 " 



(8) Lime-shale, 15 " 



(9) Sand-rock, 12 " 

 (10) Quartzite, 6 " 



This gives a total depth of 375 feet, of which 215 feet con- 

 sists of igneous rock. No. i, the only sample in the section I 

 have been able to examine, is unquestionably quartz-porphyry. 

 Of the other igneous rock cut in the shaft, No. 3 was called by 

 the Manager " Porphyry or Trachyte," Nos. 5 and 7 being 

 called porphyry similar to No. i. Between this shaft and 

 Terry's Peak yet remain the upper beds of the Potsdam (above 

 these cut in the shaft) to a thickness of possibly 275 feet, thus 

 indicating pronounced laccolitic conditions for Terry's Peak." 



The Sunset mine shaft is situated at the head of a little 

 valley which runs to the southwest from the north fork of 

 Whitetail gulch, uniting with the latter at a point a short dis- 

 tance below the horse-shoe bend, in the Elkhorn R.R. It is 

 about 1 1 50 feet lower in elevation than the summit of the 

 mountain. From data kindly communicated by Professor F. C. 

 Smith personally, and through Professor Kemp, the writer is 

 able to construct roughly the following section : 



1 Transactions of Amer. Inst. ^lin. Eng., XXVII, 410, 1897. 



