J78

engineer’s report.

predecessors, and far more likely to succeed. The only similar ma-chine in existence has recently been tried in California , where it cut a .six foot hole in hard rock at the rate of 23 inches in an hour and 45minutes, or at the rate of 26 feet per day, with one machine.”

And, in a published letter to General Wool, under date of Septem-ber 25, 1858, Mr. Hauptsays: “The slowest progress of the machine,when working, will be fifteen inches per hour; the fastest, twenty-fourinches. A machine at each end, working but half the time, with theslowest feed, should go through the mountain in twenty-six months.”

This machine, which weighed about 50 tons, and which Mr. Hauptstates cost his firm $25,000, was put in operation at the western endof the tunnel, but proved an entire failure. It never excavated a sin-gle foot of tunnel, but, after various trials, was dismantled, raised upfrom the road bed so that cars could pass under it, and now remains atthe western portal to the Hoosac, a monument of misapplied ingenuity.

Boring and tunnelling machines, therefore, in this country appear sofar to have failed to meet the expectations of their projectors.

In England, various attempts have also been made at tunnellingmachines. In 1857, Captain Pennice, of the royal engineers, con-structed one on a small scale, and it was stated that the Worcester &Hereford Railway Company had ordered one to cut a tunnel 13 feetin diameter through the Malvern Hills, which are composed of sienite,and that another was to be set at work upon the great HauensteinTunnel, through the Jura Mountains . The following is a descriptionof the machine: —

“ This machine consists of a species of steam battering-ram, or im-mense piston-rod, at the head of which a powerful wrought-iron crossis fixed, consisting of four, eight, sixteen, or twenty-four arms. Thesearms are completely studded with diamond-shaped steel points, and,by an ingenious contrivance, at every blow on the face of the rock apart of the revolution of the cross is made; thus imitating the actionof the boring tool in preparing for a blast.

“The line of diamond-head chisels on each arm is thus kept contin-ually cutting near an edge of rock, which is much more advantageousthan a blow in the centre of a solid. The diameter of the excavationmade is such as to include the whole of the machinery, which is on awheel-truck lying on the rails, and progressively follows its excavator.The progress is something like that of the Teredo Navallis, which issupposed to bore, with its horny head, a hole large enough for thebody to follow. The difficulty with a machine of this nature is, totemper the blow to the hardness of the rock which is to be cut, until