The undertaking now came into the hands of the State, by a foreclosure of the mortgage which it held as security for repayment of the loan to the Troy and Greenfield Railroad Company. The next year, 1862, a board of commissioners was appointed to investigate the condition of the enterprise, and report what action in the case was most expedient The commissioners recommended that the State should undertake the completion of the work. Their recommendation was adopted. At this time the tunnel had been excavated for a distance of 4250 feet, or about one fifth of ifs proposed length. In carrying it so far the State had advanced, in addition to what had been expended of the funds belonging to the company, $1,431,447. It was estimated by the commissioners that it would now require $3,218,323 to finish the tunnel- t will be noticed how, as its construction went on, its cost was constantly increasing. The estimate had advanced from the original mark of less than a million dollars to two millions; and now to complete it, after so much had been done, it was admitted, would require more than three times the expected cost of the whole undertaking. The engineer who now reported to the commissioners the condition of the road and tunnel, Mr. Laurie, estimated that by sinking a central shaft, and working each way from that as well as from the two ends, the tunnel could be completed in eleven years, or in 1874, which corresponded very nearly with the final result.

Work on the tunnel was resumed, under the direction of the commissioners. They undertook the sinking of the central shaft. The requisite depth of this was 1028 feet. The magnitude of the, tunnel undertaking is seen when we consider that only to sink this shaft would require four years of continuous labor and the expenditure of not less than half a million of dollars.

Meantime the work went on, with various obstacles and difficulties. As the miners penetrated farther and farther into the mountain, the labor became more and more troublesome and oppressive from the foulness of the atmosphere, resulting from lack of ventilation and the elimination of noxious gases in the process of blasting. This has always been one of the chief difficulties in tunnel construction. Hitherto, also, the work of drilling had been done by hand labor alone. We have mentioned the employment at the outset of a boring machine and its failure. Other machines were from time to time constructed, but none of them proved practically efficient. About this time, however, there had come into use in Europe various percussion drills. One, used in the construction of the Mont Cenis Tunnel under the Alps, had been introduced here, but was unsatisfactory in its working. Mr. Haupt, one of the former contractors of the tunnel, had given much thought to the matter, and had nearly completed a machine of this class, when his connection with the tunnel was brought to a close. But a percussion drill, known as the Burleigh drill, from its inventor, Mr. Charles Burleigh, of Fitchburg, was tried, and was so effective that it continued to be used until the tunnel was finished, and is now in very general employment for drilling purposes, both in this country and abroad. It is a small and quite simple machine, and contrasts strongly with the great engines which were at first constructed for use on the tunnel. It can be handled easily by one man. It consists of a cylinder with a piston to which a drill is attached. Steam or compressed air is admitted into the cylinder on the two sides of the piston alternately, as in the case of the ordinary cylinder of the locomotive, and the drill is thus driven back and forth with great rapidity. Instead of the sixty strokes a minute made by the hand drill, and then only with frequent intermissions for rest, the percussion drill makes three hundred, and without cessation until the drill is so dulled that it must be replaced by another.