Before proceeding farther we had better state that a French metre is equal to 3 feet 3·371 inches; consequently, 1,000 metres (or a kilometre) are equal to 1093·6389 English yards; an English mile is 1760 yards or 1609·31 French metres; 100 kilometres are 62¼ English miles; but a rough conversion of kilometres into English miles can always be made by multiplying the number of the former by 5 and dividing by 8; _vice versâ_ to convert English miles into kilometres—multiply the number of the former by 8 and divide by 5.
In the 25 miles, or 40 kilometres, extending from St. Michel to Lanslebourg, there is only a rise of 670 metres, or 1,994 English feet. The steepest gradient is for 2½ kilometres (1½ miles) just beyond Modane at the French entrance of the great Tunnel of the Alps, of which we shall speak presently, the rise is 1 in 19, or 278 feet in the mile; and beyond Bramans, five miles farther, there is a rise of 1 in 20, or 264 feet in the mile, for 2 kilometres. The remaining gradients are as follows—1½ kilometre, 1 in 47; 8½ kilometres (5¼ miles) 1 in 60; 4½ kilometres (nearly 3 miles) 1 in 100; 7½ kilometres (4¾ miles) 1 in 108. In fact, with the exception of 4 kilometres (2½ miles) post-horses go at the trot over the whole distance between St. Michel and Lanslebourg. It is at this latter place that the real elevation of the pass commences, and the traveller who wishes to see a considerable portion of the ascent that is before him, can do so by taking a look out of the comfortless-looking, but, in reality, comfortable _Hotel Imperial_, the ground-floor of which is occupied as a refreshment room for passengers, and by _Messieurs les Employés de la Douane Imperiale de la France_. The frontier which separates France from Italy is exactly at the summit of the pass, and it is 10,500 metres or 6⅓ miles from Lanslebourg. In these 6⅓ miles it is necessary to mount 2,171 feet, or at the continuous rate of 350 feet in the mile. The gradient is consequently 1 in 15 in the whole of these 6⅓ miles. From the summit to L’Hospice, 4⅕ kilometres along the bank of the Cenis Lake, which yields capital trout six months in the year, and is frozen over for the other six, the gradient falls 1 in 25, or 211 feet in the mile. There is a short length of 3 kilometres to the Posting House of La Grande Croix, with a gradient of 1 in 60, or 88 feet in the mile. The severest gradient on the whole pass is in the next 10 kilometres (6¼ miles), 1 in 14, or 376 feet to the mile; and from Molaretta to Susa, 10⅓ kilometres (6½ miles), it is not much better, being 1 in 15, or 350 feet in the mile. There is a difference in the comparative elevations above the sea, of St. Michel and Susa of 715 feet, Susa being the lower of the two. Consequently, the Italian side of the pass is more precipitous than the French, for, whereas the total rise from St. Michel to the summit (a distance of 31 miles) is 4,165 feet, the descent from the summit to Susa (a distance of 18 miles) is 4,880 feet; in fact, the descent of the mountain only terminates as the town is entered. Of course, what are ascent and descent when going from France to Italy are reversed when coming in the opposite direction.