Much interesting knowledge in this caption was lately given by James Hayward, engineer, on the examination before the Massachusetts Committee respecting the Hoosac Tunnel. He has visited Europe, and examined as many as thirty tunnels. During his visit he made the acquaintance of several eminent engineers and supplied himself with profiles of several tunnels. The Marseilles tunnel, located at Nerthe, near Marseilles, is three miles (15.153 feet) long, and has twenty-four shafts. The material in this tunnel is a very hard limestone. The height of the ground over it is a little over 600 feet. The aggregate length of all the shafts is 7,589 feet ; the deepest shaft is 610 feet. The cost per yard down is 143, The shafts are nine feet in diameter, and are lined with masonry, at a cost of $19'40 per yard down. Mr. Hayward obtained from the engineer in charge of the work, the prices which the work cost. The deepest shaft cost $73 per yard down;- entirely completed. The entire ? cost of all the shafts, for the masonry, amounted to $47,000; and $150,000 for the whole cost of the tunnel. The entire cost of the tunnel to the contractor was $125 for the, lineal yard ; this includes shafts. The tunnel was lined with masonry of different thicknesses, which cost $423,000. The cost of the tunnel, exclusive of the masonry was $705,000. The contractor, however, gave Mr. Hayward a less price, about 4 per cent., as having been the actual cost. The Woodbood Twmel between and Sheffield is a little over three miles long, and the hill over is 600 feet high. It has five shafts, 10 feet in diameter, which vary from 400 to 600 feet in depth. The character of the rock is granitic, not so hard as our granite ; it is called there " mill stone rock." The tunnel was about five years in construction, and its whole cost was $1,026,-705. The Box tunnel is one of the earliest as also the largest and most expensive tunnel ever constructed, it is 39 feet high and over 30 feet wide. The tunnel is on the Great Western Railway, about 100 miles from London. The shafts were 25 feet in diameter, its length is 9,576 feet. Over some third of it is through the solid rock. In England there are on the canals some forty miles of tunnels—the one on the Hud-dcrsfield canal being over three miles in length, and through a substance much more flinty than the Hoosac Mountain. A tunnel is being constructed under Mount Cenis, in the Alps, which, when finished, will be about seven miles in length ; and another of equal distance under the Appenines, on the route of the railway from Turin to Geneva. There are numerous tunnels on the Baltimore and Ohio Railroad, and the branch road to Par-kersburg. The highest cost of excavating the tunnels on the Baltimore and Ohio Railroad, which penetrates mica rock, was three dollars eighty-seven cents per yard, and at this rate it will cost over one million three hundred thousand dollars to perforate the Hoosac Mountain. The proposed tunnel will be about four miles and a half in length, and the number of cubic yards of stone to be removed some 450,-000.