THE VICINITY OF LA PORTE AND GIBSONVILLE. 



451 



has been explored and worked by drifting. The works extend nearly to the northeastern boundary 

 of the property. There are two principal tunnels, the upper one being nearly a mile in length, 

 though not straight. The main thoroughfare in the upper tunnel follows for 1,700 feet a course 

 N. 60° E. then N. 73° E., for 800 feet, N. 43° E, 900 feet, and, finally, N. 17° W., 1,300 feet. 

 The bearings are all magnetic.) The grade of the tunnel in the four sections is, respectively, If, 

 7 A 51 and 6 inches for every twelve feet. The total rise in the tunnel, according to these data, 

 would be 152 feet. At a point 1,500 feet from the mouth of the tunnel a shaft was raised 337 

 feet to the surface. The strata in this shaft were reported to me to be as follows : Sixty to seventy 

 feet of white quartz gravel, forty feet of clay with gravel streaks, seven to eight feet of gravel and 

 sand, one hundred and eighty to one hundred and ninety feet of pipeclay, and forty feet of sur- 

 face dirt, volcanic tufa, and the like. The drifts take about three and a half feet of the gravel, and 

 from six to fourteen inches of bed-rock. The gravel is a white quartz, rather smooth, but not 

 so well rounded and polished as that of La Porte. There is also a great deal of clayey material 

 mixed with the gravel, amounting in places to as much as a quarter or a half of the whole deposit. 

 The pay-streak contains frequent fragments of float bed-rock and clay boulders, which appear to 

 be the result of the decomposition of slate boulders. Specimens 93 and 94 are from this place. 

 These clay boulders vary in size from a few inches up to several feet in diameter. Large quartz 

 boulders from twenty to forty feet in diameter, are also met with. The width of the channel, 

 where drifted, is live or six hundred feet, but is from seven hundred to one thousand feet between 



The gold is coarse, pieces weighing as much as ten ounces being sometimes found,* The 

 average fineness of the gold is said to be from .916 to .918. The yield of this gravel was re- 



nins. 



ported to me as $ 1.50 per car-load, reckoning everything brought from the mine. The cars hold 

 about a cubic yard of loose dirt, representing perhaps half a cubic yard of gravel in place. I 

 was also told that a shaft had been raised in the gravel of the upper workings, by Mr. Morgan, 

 through seventy feet of gravel, the average yield of which was 62^ cents per cubic yard. 



The bed-rock of this district is slate, with the exception of the serpentine belt, which lias already 

 been referred to as crossing in a northerly direction by Whiskey Diggings. Under the gravel the 

 slate is usually very soft and full of crevices, or is changed to a depth of several feet to a clay 

 similar to that described as seen at La Porte and Secret Diggings. 



The fall in the bed-rock is quite rapid fron Ilepsidam to Gibsonville, The altitude of the upper 

 tunnel, at its mouth, at the Niagara mine, I made to be G,000 feet ; the mouth of the lower tunnel 

 is 106 'feet lower. Changes in the level of bed-rock are frequent and sudden. The upper tunnel 

 for 1 500 feet is all in slate bed-rock ; though a point a, hundred feet to the northwest of the mouth, 

 and on the same level, would be forty or fifty feet above bed-rock. In the mine there are sudden 

 changes of level, or " jumps," amounting to three or four feet at a time, and indicating the former 

 existence of cascades or rapids. At Mount Pleasant I found the altitude of the bed-rock to be 

 5 5G0 feet and at Gibsonville, 5,420. There is thus a fall of over 600 feet in about three 

 miles. The gravel is nearly continuous for this distance, excepting where it has been cut across 

 by Whiskey Creek. The opinion is stoutly held by some among the miners thai, there is also a 

 back channel farther to the northwest, and hidden under the lava. It is said, for instance, that 

 in the Union claim the northwestern rim is crest-like, and on the farther side has a pitch to the 

 northwest, and that upon this sloping surface coarse gold was found in connection with boulders, 

 sand, vegetable matter, and some quartz gravel, the whole being quite different in appearance from 

 the deposit in the main channel. On the whole, I do not regard the evidence in favor of the 

 existence of a back channel as very strong. 



The two difficult questions which arise in regard to this piece of channel are, — where did it 

 find an outlet] and from what direction did it come? There is high slate-rock to the southeast 



* A specimen selected from the stock on hand, as a ''fair average nugget," weighs a quarter of an ounce. 

 It is three quarters of an inch long by half an inch wide, and is of irregular thickness. It lias numerous 

 small angular fragments of quartz imbedded in it, and its angles and edges are all more or less rounded by 



abrasion. 



