feet deep with a bridge built between two projecting craigs at opposite sides of the ravine, whilst other bridges, of almost adamantine strength, and hundreds of feet in length, are often barely sufficient to resist the giant force of the torrents that dash along the gorge, and at times rise to within a few inches of a bridge’s level. And when the road is finished, at the heavy cost which all such works involve, and traffic is brought upon it, its length is very different from what it would have been if it could simply have been climbed up the mountain by the shortest and straightest possible way, and then been brought down again in the same manner. Still greater will be the difference between it and what our friend the crow accomplishes in the flight we have just referred to. The experience acquired by our engineers tells us that the very maximum gradient an engine on the ordinary principle can climb up is 1 in 25, or 211 feet in a mile, but this can only be for a few yards, and with what is known, in locomotive language, as “a good run at it.” On the Sœmmering, as has already been stated, the average gradient on the north side is 1 in 47, or 111 feet in a mile; on the south side 1 in 50, or 105 feet in the mile; yet these gradients, favourable as they are, compared with the gradient of an ordinary roadway over a high mountain pass, could only be obtained at a cost of £98,000 a mile. Equally costly was the Giovi incline, constructed to surmount the Apennines near to Genoa. The worst gradient on it for a short distance is 1 in 29, or 160 feet in a mile; its best 1 in 50, or 106 feet in a mile. The ruling gradient of the beautiful railway over the Apennines between Pistoja and Bologna is 1 in 40, or 132 feet to the mile. The distance from Pistoja at the foot of the mountain on the east to Poretta at the foot of the mountain on the west, by the old road, is 25 “_chiliometres_” (kilometres), a little more than 15½ English miles, but in order to obtain for the railway the average gradient of 1 in 40 we have just mentioned, it has been necessary to extend the distance from 25 chiliometres to 40, equal to 25 English miles. Each of these 40 chiliometres has cost 1,000,000 francs, or £40,000, making the total cost of the railway independent of the special rolling stock for working it, £1,600,000, or at the rate of £64,000 a mile. If at the time that Mr. Fell was engaged in connection with the construction of this very fine work, he had had his ideas matured respecting the centre-rail system, and that consent had been given to the line being laid down in accordance with it, the distance to traverse would have only been 15½ English miles; many expensive works would have been avoided, and the total cost of the line would not have exceeded £400,000—probably it would have been considerably less. Another matter worthy of consideration is, that this Apennine Railway consumed eleven years in its construction. Not very protracted, considering that there