There are few tunnels of any length in the United States. The Cincinnati Tunnel is 3,337 yards long; the Kingwood 1,366. The Alleghany mountains are perforated by one, the property of the Pennsylvania Railroad Company, which is 1,204 yards long, 24 feet wide, and 22 feet high. There are four through the Blue Ridge Mountains, Virginia, the longest of which is 1,955 yards, the next 1,418 yards, with an uniform gradient of 1 in 70. The Long Duck Tunnel, New Jersey, is 1,437 yards in length. But the Hoosac Tunnel, Massachusetts, will, when completed, be the longest railway tunnel in existence—except the tunnel of the Alps—8,166 yards; it was commenced in 1855, but it has only been vigorously proceeded with since 1864; its total estimated cost is to be £1,100,000, of which about £420,000 have been expended upon the 2,350 yards already constructed; its width is 26 feet, height 24 feet; the rock through which it is pierced is mica slate mixed with a little quartz.[132]
General Haupt, of the United States Army, the engineer-in-chief of this tunnel, is said, by the _Times_, to have invented one of the most compact, effective, and economical drilling machines, applicable for boring tunnels, driving adits of mines, and indeed for every description of work in which the hardest kinds of rocks have to be pierced. It is stated that it can drive holes in granite, or even quartz, at the rate of nearly four inches in a minute, and that as soon as about twenty-eight inches have been drilled, the blasts take place, when the machine can, in consequence of its great lightness and portability, be immediately carried over the _debris_ caused by the explosion, and be at work upon the new face of the tunnel in the course of a few minutes.
We extract the “latest novelty” in tunnels from a New Zealand newspaper received in England August 1867,—
“A TUNNEL THROUGH AN EXTINCT VOLCANO.—The Moorhouse Tunnel, opening up the fertile plains of the Canterbury settlement, is 2,838 yards long, and cost £195,000. It affords, we believe, the first instance where a complete section of an extinct volcano has been opened out. The elaborate drawings prepared by Dr. Haas for exhibition in Paris, will draw the attention of geologists to the fact, and doubtless afford the greatest satisfaction to the scientific world. The rock in the tunnel may be described as a series of lava streams and beds of tufa, intersected by vertical dykes of phonolite. The lava streams consist generally of scoria, overlaying a coarse pink trachyte, which passes gradually through shades of grey, purple, and blue into a black finely grained dolorite intensely hard and tough; the lightest and softest rock being at the top, and the densest and blackest at the bottom. Regarded from an engineering point of view, the work is considered eminently successful.”