604 MINING INDUSTEY. 



The Burleigh tunnel is in Sherman Mountain, a quarter or half-mile east 

 of the Terrible mine. Its mouth is not far above the bed of the stream. It 

 enters the hill on a course of north 15° west, or nearly at a right-angle to the 

 general course of the veins. It is 9 J feet wide and 74 feet high. In August, 

 1869, it had been driven 120 feet through hard, granitic, and gneissic rock, 

 without having found anything of value. It has since been driven on contin- 

 uously, and, according to newspaper reports, has developed some ore-bearing 

 veins. The mountain rises steeply above the tunnel, reaching an altitude at 

 the summit of about 2,000 feet, so that any veins thus cut will be opened at 

 considerable depths below their outcrops. This enterprise is under the man- 

 agement of Mr. Burleigh, the inventor of the drilling machine which bears his 

 name. This machine is employed in the tunnel, and is said to have proved 

 itself here, as elsewhere, a most useful instrument in this kind of work. The 

 details of its construction are too intricate to be intelhgibly explained with- 

 out drawings. It is, however, ingeniously and effectively contrived, perform- 

 ing its duty with comparatively little expense for repair. It is driven by com- 

 pressed air, which, escaping from the machine at every movement of the drill, 

 affords the great advantage of good ventilation. In the Burleigh tunnel a 

 track is laid, on which a carriage is placed. This vehicle carries four drilling 

 machines, which are so attached to the point of support that they may be fixed 

 at any angle, thus directing the point of the drill against the face of the rock 

 at any desired inclination. The drill strikes 250 blows per minute. When 

 a sufficient number of holes have been drilled the carriage is run out, the 

 holes charged and fired, and the rock thrown aside, so that the carriage may 

 return to the heading; after which the rock is removed from the tunnel. 



The air compressors are at the mouth of the tunnel, consisting of two 

 sets, or four air cylinders, 12 inches in diameter by 16 inches in length; and 

 two steam cylinders, 9 inches by 16 inches. There is also a conveniently- 

 arranged machine shop, supplied with necessary appliances for the construc- 

 tion and repair of drilling and other tools. The progress of this tunnel, up to 

 the date referred to, was two feet per day. 



The Baltimore tunnel, or, more properly, the tunnel of the National Sil- 

 ver Mining Company, is further up the valley, a half-mile west of the Brown 

 and Terrible mines. It is favorably situated, where the slope of the hill-side 



