The galleries and tunnel, as well as the siege-works, are illustrated by two plates, No. 31 and 32 of the Appendix. The tunnel was about 550 yards long. During M. Cessac’s investigation the timber which supported part of it still existed.
The earliest mention that we have of tunnelling in connection with the Alps dates back more than 400 years. Anne,[125] Duchess of Savoy, conceived the grand project of piercing the Col di Tenda, then, and for nearly two centuries and a-half afterwards, the best and easiest pass available between France and north-western Italy, with a tunnel at about one-third of its height from the summit. It appears, beyond doubt, that the works were begun, but at the death of Anne they were abandoned; after a lapse of three centuries they were resumed in 1782 by order of Victor Amadeus III., King of Savoy. The excavation of the mountain was continued, although not vigorously, until 1794, when it was abandoned, in consequence of the invasion of Savoy by the French. The total length of the tunnel would have been about 3,000 yards, and by means of it a precipitous sugar-loaf ascent of 1,300 feet to the top of the pass would have been avoided. At the present time the idea of the tunnel is revived, it being proposed to construct to it a railway on the Fell system,[126] from Cuneo at the foot of the pass, which place is now connected with Turin and the whole system of Italian railways by a line fifty-four miles long. The Cuneo district is one of the most productive of the fertile plains that fringe the southern slopes of the Alps, and extend for a width of from fifty to sixty miles beyond them.
We did not begin either to make canals or to tunnel in Great Britain until a little more than a century ago. Now we have 2,200 miles of inland navigation, of which 213 are in Scotland and 297 in Ireland. Brindley, the engineer of the Duke of Bridgewater, commenced the Harecastle Tunnel on the Trent and Mersey Canal in 1765, but it took him eleven years to finish it. It was not until 1776 that the first boat was able to go through it. The tunnel is 2,880 yards long, 12 feet wide and 9 feet high. Although Brindley was much troubled with quicksands, the work was completed for the marvellously small sum of £3. 10s. 8d. a yard forward. Some years afterwards, in consequence of the immense increase of the business of the canal, Telford constructed another Harecastle Canal alongside the first, the dimensions of which are—length, 2,936 yards; width, 14 feet; height, 16 feet.