the Congressional Committee on Mines and Mining in 1872, Adolph Sutro of the Sutro tunnel said:  “The deepest hole dug by man since the world has existed is only 2,700 feet deep, and it remains for the youngest nation on earth to contribute more 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 was encountered than could be hoisted out in the “skips” with the dirt.  At the 2,200 level two Cornish pumps, each with columns fifteen inches in diameter, were put in.  At the 2,400 level the same pumps were used.  On this level a drift was run that connected with the old