184 



THE AUEIFEEOUS GEAVELS OF THE SIEEEA NEVADA. 



The prominent point just north of Nevada City, known as the Sugar Loaf 

 (as already mentioned), is 3,111 feet above the sea level, and 670 feet above 

 the bed of Deer Creek at the Suspension Bridge. The extension westerly 

 of the volcanic ridge, on which the Sugar Loaf forms a partly isolated and 

 therefore rather conspicuous mass, is called Cement Ridge. Its general 

 direction just beyond the gap which separates the portions of the ridge, is 

 S. 21° W. (magnetic), but a mile or so farther on it becomes more nearly 

 west. Cement Hill is a few feet lower than the Sugar Loaf, directly opposite 

 which it seems to form almost a flat table of lava, sloping off gradually to- 

 ward the west. Dean's Tunnel is on the northwest quarter of Section 1 (T. 9 

 ft. ; R. 16 %), about two miles northwest of the centre of Nevada City. Tbe 

 course of this tunnel is a little west of south, and it is run in a much decom- 

 posed syenitic granite, resembling the usual bed-rock in this vicinity. This 

 granite has undergone decomposition in a very irregular manner; so that, on 



the line of the tunnel, there are still " boulders," 



tions of the rock are called, 



as the undecomposed por- 



which cannot be removed by the use of pick 



and shovel, as the rest of the material can be. This tunnel had been driven 

 400 feet at the time when visited by us ; but another one, forty-three feet 

 higher up, had been carried in for a distance of 900 feet on the bed-rock, 

 before striking the gravel. This higher tunnel was not low enough, to strike 

 the channel, but was run 575 feet in the gravel without having got entirely 

 across it. The question of the connection of the channel here with that of 

 the mines east of the Sugar Loaf, known as the Manzanita Diving's, is one 

 of very considerable difficulty. The following extract from Professor Pettee's 

 notes gives the results to which he was led by his examinations in this 



region : 



In exploring the Cement Hill Ridge, in the direction of Peck's Diggings, nothing but volcanic 

 was seen until I began to descend the spur between Long Tom and Native American ravines ; 

 and here, about 700 or 800 feet south of Peck's house, the end of the lava was reached, this alti- 

 tude being about 2,700 feet. The measurement of the lower edge of lava on Cement Hill, oppo- 

 site the Sugar Loaf, had given me as a result 2,835 feet. Peck's house is on the unsurveyed land, 

 but he said the corner stake between sections 2, 3 (and what would have been and will be when 

 sectionized), 34 and 35, was between a quarter and half a mile pretty nearly due south of his 

 house. Long Tom Ravine is on the east, and Native American Ravine on the west of Peck's ; 

 into the last-named of which his old diggings, which are mostly open excavations, discharge. He 

 selected a spot for me which was nearly an average bed-rock, and the barometer indicated an alti- 

 tude of 2,632 feet, which is only about twenty feet lower than the bed-rock in the Manzanita 

 Diggings. A difference so small as this was unexpected (though there were some who declared 

 that the bed-rock at Peck's was even higher than at the Manzanita Diggings), and I am sorry that 

 arrangements were not made to have a short series of synchronous observations at the two places, 

 extending over three or four hours. The distance between the two places is not far from three 



