Facts and Figures Concerning the Hoosac Tunnel

by John J. Piper

But it is not eight hundred horse power, nor four hundred that is required to operate the drilling machinery and ventilate the tunnel; for two hundred and eight horse power is all that has ever been used or needed at Mt. Cenis. This leaves a pretty wide margin for drouths, evaporation, and other contingencies.

In his observations upon the power required, Mr. Bird becomes severe and sarcastic. He assails the opinion of the commissioners that "the loss of power by carrying the compressed air through five miles of pipe will be quite insignificant," and after asserting that there are no data by which to test the correctness of this opinion, and claiming "some experience in such matters," prefers that such an "experiment". should be tried with somebody's money besides his own. It is gratifying to learn from Mr. Bird, himself, that he he has had experience in the matter of compressed air as a motive power, and that a "cussed furriner," as he elegantly phrases it is not to be allowed to bear off the palm of this great discovery uncontested. Doubtless M. Sommeiller will yield to the superior science and sagacity of Mr. Bird; but our countryman should lose no time in informing his fellow citizens of his investigations, experiments and success in arriving at the conclusion that compressed air cannot "be carried through five miles of pipe without a very serious loss of power through friction, leakage, &c." But, unfortunately for this view of the case, there are data establishing the fact that compressed air has been conveyed through more than two miles of pipe at Mt. Cenis, and then operated the drills without any appreciable loss of power. If there is no loss in two miles, how can there be in five? It is no longer an experiment, but an established scientific fact.

The size of the present excavation next engages the attention of our observer, and he calls the commissioners to account because they have not followed their own recommendation to excavate the Tunnel to its full dimensions as the work proceeds. Since their recommendation was made in the winter of 1863, the commissioners have had much experience, and the price of labor has doubled. Only a small number of men can work on a heading, but when a heading has been advanced a large number of workmen can follow rapidly in enlarging the excavation, and will soon overtake those engaged on the heading. At Mt. Cenis, the pneumatic drills are only used on the heading, and the enlargement is done by numerous laborers with hand drills. It is apparent that the commissioners have been actuated solely by motives of economy in prosecuting the heading alone, at the present high rates of labor. The work of enlargement is comparatively easy and rapid, and might well await a decline in the cost of labor, though it must be admitted that the importance of completing this noble work, ought to outweigh the consideration of any possible cost.

On the subject of pneumatic drills, Mr. Bird is emphatic. He says, "no intelligent man puts the slightest confidence in the successful working of any borer, or drill, in the rock of the Hoosac Mountain, unless operated by hand. In a strictly homogeneous rock, machine drills might work, but in a rock like the Hoosac, where the drills, working generally in a comparatively soft material, are liable at any moment to strike veins of quartz, and where a part of the hole will be in the slate and the rest in quartz, no machine drill has yet been found to stand." This reckless and false assertion is made in utter defiance of Mr. Storrow's report and all other authorities upon the Alps Tunnel, which has now been excavated nearly four miles with machine drills on the heading. Mr. Storrow says that masonry is used because the rock "is not homogeneous in character. I stood at the front of the machines, watching them for three quarters of an hour. One drill was driving directly into hard quartz, advancing very slowly, and making the sparks fly at every stroke. Others working in softer spots, were cutting rapidly."

Mr. Bird has much to learn about pneumatic drills, and, without going beyond the borders of Massachusetts, he can see a drill operate by compressed air, so indifferent as to the character of the rock it works upon, that it will penetrate the hardest granite and the composite rock of the Hoosac with the same facility, and at a rate which would astonish even M. Sommeiller.

The figures upon which Bird bases a "calculation" as to the time of completing the Tunnel, are as far from being correct as his general statements are from the truth. One example is enough to illustrate, and by this the reader may fairly judge what the "calculation" is worth. He says the total length of the Tunnel is 24,586 feet, when the fact is that it is 25,586 feet. This is no mistake of the printer, for the figures repeatedly occur in the pamphlet, and always the same; and it is with this gross blunder that the "calculation" sets out. The truth is that any careful reader of this article, is a Better judge of the whole subject than Mr. Bird, because he will have reliable dates, facts and figures, by the aid of which he can make a calculation for himself, or' form an opinion as to the time within which the work can be done, which will be quite as likely to be correct as any, "I undertake to say," of the oracular Bird.

On the 1st of December, 1865, the penetration at the East end was 2904 feet; at the East heading of Western shaft, 414 feet; West heading of same shaft, 280 feet; at West end heading, 756 in the whole, 4354 feet. The central shaft had been sunk two hundred and twenty feet. The average progress on this shaft during the months of August, September, October and November was 18 3-4 feet per month. Assuming this for the average in December, January and February the shaft was 275 feet deep, on the 1st of March, the whole depth to grade being 1037 feet. The average progress on the East face of Western shaft was sixty-three feet per month. Allowing that average for December, January and February, and the penetration on this face is now more than 600 feet. The average on East end was forty-four feet. Add this average for the last three months, and the penetration at this end is now 3036 feet, and the total penetration 4675 feet, with 575 feet of shaft sunk.

Mr. Laurie states in his report that in the ten tunnels which he names, in this country and Europe, the average progress made on each face from a shaft was thirty-eight feet, and on the end faces fifty-four feet per month. Let the intelligent man who forms opinions and conclusions for himself, compare the statistics which have been given in the course of this writing in relation to tunneling in Europe and in this country, and then, taking into consideration the inadequate means which have, until recently, been applied to the Hoosac enterprise, and surveying the progress which has been made whenever the work was prosecuted with vigor, let him judge how soon, and at what cost, the Tunnel may be completed, even without the aid of machine drills.