The trial of machinery at the Hoosac tunnel, upon the Troy and Greenfield Railroad, has not been favorable to its employment. This tunnel will be four and three-quarter miles long. Originally projected with a width of 24 feet, and a height of 20 feet, it has been contracted to 14 feet wide, and 18 feet high. The estimated cost was $2,696,229. The rate first assumed was $137 per running foot. The rate per cubic yard varies from $5 to $22, and $30, for the excavation of shafts. The contract prices for the Hoosac tunnel, in 1869, were as follows: Tunnel enlargement, per yard $ 16.00 Heading enlargement, east end, per yard 9.00 Heading enlargement, west end, per yard 9.75 Full size tunnel extension, east end, per yard 11.00 “ “ west end, per yard 12.00 “ “ central section, per yard 14.00 Central drain, with air and water pipes complete, per lineal foot 13.00 Sinking shaft (27 × 15), per foot, depth 395.00 Pipes (10 inch), set in shaft 6.00 Arching (in brick at $9 per M), per M 22.00 Excavating and constructing 50 lineal feet of stone arch, and filling 23,000.00 Although more than two hundred railroad tunnels have been constructed in the United States, and an unknown number of canal tunnels, facts in regard to them are difficult of access. Recent bids for tunnel work upon United States railroads have been offered at $5.40 per cubic yard for excavations. Canal tunnels, of the ordinary dimensions of 297 square feet area, would cost $113.20 per running foot. The uncertainty of the nature of tunnel excavation, the unexpected difficulties to be overcome, baffle all anticipatory estimate. The variable rates in the preceding tables establish this fact. The average cost per running yard upon French canals is about $152, which sum probably includes arching. Rates of labor in the United States would increase the cost about four times this amount. Comparing the contract price of American tunnels, as given above, with the table of English tunnels, and bearing in mind that the cost of arching is included in the latter, we find in Nos. 3, 6, and 9, the cost of English tunnels is in excess; number 3 being nearly double, and number 9 one-tenth more, while, in every other case, the cost at American rates is greater, varying from one-third to five and one-half times more.