to science and geology by giving
opportunities of studying the formation of mineral veins at a greater
depth than has ever been accomplished by any other nation in the
world." Mr. Sutro was of the opinion that the completion of his tunnel
would enable our leading mining companies to reach a vertical depth of
5,000 feet.

This great depth has never yet been attained except in a bore hole or
artesian well. The deepest points to which the crust of the earth has
ever been penetrated have been by means of such borings in quest of
salt, coal, or water. A bore hole for salt at Probst Jesar, near
Lubtheen, for the Government of Mecklenberg-Schwerin, is down 3,315
feet, the size of which bore is twelve inches at the top and three
inches at the bottom. A bore hole was put down for the Prussian
Government to the depth of 4,183 feet. But in these bore holes the
United States leads the world, as there is one near St. Louis, Mo.,
that is 5,500 feet in depth. Here on the Comstock, in the Union
Consolidated mine, a depth of 3,300 feet has been attained, but not by
means of a single vertical shaft. The vertical depth of the shaft is
2,900 feet; the remainder of the depth has been attained by means of
winzes sunk from drifts. Several long drifts were run at this great
depth without difficulty as regards ventilation or heat.

The combination shaft is situated much further east (in which
direction the lode dips) than any other on the Comstock. It is 3,000
feet east of the point where the great vein crops out on the side of
Mount Davidson; 2,200 feet east of the old Chollar-Potosi shaft, 1,800
ft. east of the old Hale & Norcross (or Fair) shaft, and 2,000 ft.
east of the Savage shaft. Thus, it will be seen it is far out to the
front in the country toward which the vein is going. The shaft is sunk
in a very hard rock (andesite), every foot of which requires to be
blasted. The opening is about thirty feet in length by ten feet in
width. In timbering up this is divided into four different
compartments, some for the hoisting and some for the pumping
machinery, thus presenting the appearance at the top of four small
shafts set in a row. Over the shaft stand several large buildings, all
filled with ponderous machinery.

The Sutro drain tunnel (nearly four miles in length) connects with the
shaft at a depth of 1,600 ft., up to which point all the water
encountered below is pumped. The shaft was sunk to the depth of 2,200
ft. before more water