Twenty years ago very few mining shafts in the world had reached a depth of 2,000 feet. The very deepest at that time was in a metalliferous mine in Hanover, which had been carried down 2,900 feet; but this was probably not a single perpendicular shaft. Two vertical shafts near Gilly, in Belgium, are sunk to the depth of 2,847 feet. At this point they are connected by a drift, from which an exploring shaft or winze is sunk to a further depth of 666 feet, and from that again was put down a bore hole 49 feet in depth, making the total depth reached 3,562 feet. As the bore hole did not reach the seam of coal sought for, they returned and resumed operations at the 2,847 level. In Europe it is thought worthy of particular note that there are vertical shafts of the following depths: Feet. Eimkert's shaft of the Luganer Coal Mining Company, Saxony 2,653 Sampson shaft of the Oberhartz silver mine, near St. Andreasberg, Hanover. 2,437 The hoisting shaft of the Rosebridge Colliery, near Wigan, Lancashire, England. 2,458 Shaft of the coal mines of St. Luke, near St. Chaumont, France. 2,253 Amelia shaft, Shemnitz, Hungary. 1,782 The No. 1 Camphausen shaft, near Fishbach, in the department of the Saarbruck Collieries, Prussia. 1,650 Now, taking the mines of the Comstock for a distance of over a mile--from the Utah on the north to the Alto on the south--there is hardly a mine that is not down over 2,500 feet, and most of the shafts are deeper than those mentioned above; while the Union Consolidated shaft has a vertical depth of 2,900 feet, and the Yellow Jacket a depth of 3,030 feet. In his closing argument before 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.