The object of this work is to connect France and Italy, by a continuous line of railroad, by piercing the great Alpine barrier which separates Savoy from Piedmont, and thus connecting the valleys of Rochmolles and the Arc. When the scheme was first suggested it seemed like a dream of enthusiasts. The distance would be more than seven miles. No shaft could be sunk, as it was estimated that it would take forty years to reach by that means the line of the axis of the tunnel. The gallery must then be constructed by horizontal cutting from the two ends. How were the workmen to breathe? What chasms, unfathomable abysses and resistless torrents might not be encountered? Was it certain that the two sections commenced from the opposite ends would not miss and pass each other in the middle of the mountain? But as the subject was more thoroughly discussed, these doubts and fears seem gradually to have faded away, and a conviction took possession of the public mind that such a tunnel was practicable. This conviction at last assumed form and development through the genius of Messrs. Sommeiller, Grattoni and Grandis, three young Italian engineers, who have won for themselves a nobler fame than that of either of the great generals who led their armies over the Alps. It was their good fortune to have secured the confidence of one of the most enlightened statesmen of modern times, Count Cavour, the energetic minister of Victor Emanuel, who, throughout all the doubts, perplexities and embarrassments attending the first stage of a new and bold enterprise, exposed to criticisms, sometimes ignorant, sometimes malevolent, on the part of politicians and professional men, gave these engineers his "constant, earnest and sanguine support and encouragement." It appears that an English engineer had patented a machine for drilling by steam, by means of which the drills were darted forward against the opposing rock with great velocity and force. But steam could not be used in the tunnel, where the great desideratum is a supply of fresh air. In the meantime Messrs. Sommeiller, Grattoni and Grandis had turned their attention to the question of compressed air as a motive power, and after a long series of experiments; gave to the world as the result of their joint ingenuity, a machine which acts simply by the force of air reduced to one-sixth of its ordinary volume, by means of the pressure of water. The quick perception and practical genius of our three engineers soon enabled them to combine their machine with the perforating apparatus above named, so that the compressed air took the place of steam, and performed its work perfectly. This combination is the machine which has been in successful operation under the Alps since June, 1861, and which, greatly improved and perfected by Yankee ingenuity, is about to be applied to the Hoosac Mountain.