65

D.—2,

believe the line is developed in length to reduce the gradients. There is a further rise within the tunnel for the purposes of drainage. The summit can be little if any lower than 4,000 feet. On the southern side the line rises from the chief town of the Canton of Ticino, Bellinzona, near Lago Maggiore, 729 feet, to Airolo, 3,867 feet, a rise of 3,138 feet in thirty-six miles, an average gradient of lin 60. Some part of the ascent is through ground so rough and steep that, before reaching the great tunnel, two spiral tunnels are employed to develop the line in length, and thus moderate the gradients. The Brennerbahn rises from Inspruck, capital of the Austrian Tyrol, 1,640 feet, to the Brenner Pass, 4,485 feet, in 29 miles, an average gradient of lin 54. The descent (4,185 feet) by the Adige Valley to Verona, on the edge of the Lombard plain (300 feet), is accomplished in 148 miles. The bulk of the descent is between the pass and Botzen or Bolsans (820 feet). 3,665 feet in 56 miles, average gradient 1 in 80. I have no certain knowledge of the height of the entrances to the Mount Cenis tunnel, but, from the heights of the mountains, the necessary breadth of their bases, and the length of the tunnel (about seven miles), it is certain the entrances and summit cannot be much lower than those of the Glotthard tunnel (length about nine miles). Height of Grotthard Pass, 6,934 feet. Two Italian lines cross the Apennines by open passes. I have travelled several times on the railway between Bologna and Florence. I believe the height of the pass to be about 2,500 feet. The gradients are severe on both sides, especially the southern descent to Pistoja. Bologna is on the level of the canal navigation of the plain of the Po, and the ascent, which is about twenty-five miles in, length, begins not far from the city. One of the peaks at about eleven miles westward from the pass rises to 7,000 feet, and a pass on the direct road from Bologna to Morence, fifteen miles to the eastward of that crossed by the railway, is 3,200 feet high. It is not here intended to argue that a high summit is an unimportant matter. In the notes next following it is attempted to point out when and how far it is an evil. What has been just stated goes only to show that high summits are not held to be prohibitory, and are freely accepted in mountainous countries, and permanently worked if tolerable gradients can be obtained. On most of the railways above referred to the main traffic crosses the pass in each case. There is no merely descending tonnage of importance.

APPENDIX 0-3. Mechanical and Economic Objections to High Summits. The real technical objection to a high summit on a railway is not climatic but mechanical and economic. It may increase the cost of haulage to a very serious extent, and under some circumstances may impair the safety of the traffic. It is now to be considered how far the high summit on the central line is open to either of these objections. For, in*the first place, the high summit is not necessarily an evil. If it be attained within certain limits as to gradient by a practically-continuous rise, that is to say, without reverse gradients, and without employing ill-conditioned curves, and if the heavy traffic the line carries descends for the most part on one side or the other, and does not mount, it may even be an economical advantage, and does not affect the safe-working of the line. The familiar case of colliery inclined planes, on which the loaded wagons descending from the pit's mouth draw up the empties by a rope passed over a pulley at the summit, is an extreme instance; but the advantage of a descending heavy traffic is not confined to such cases, where the descending and mounting trains are connected and partly balance each other. Suppose a case where the ascent requires exactly double the tractive force needed to draw a given load at a given pace on the level. Half the force is employed in overcoming friction, &c, the other half in overcoming gravitation. When a train has arrived at the summit there will be no engine-power needed to bring it down : gravitation will give it in descending a greater speed than the locomotive gave it in mounting —a greater speed because gravitation is a force supplied by a stationary engine—the carth —which has not to drag about its own weight, and is constant at all speeds on the same gradient, its effect being limited only by the increasing friction of the train as speed increases ; whilst a locomotive's own weight absorbs more and more of its own force as speed and friction increase, and has less effective balance for the traction of the train as more is required. But it will do more than this. Whatever additional load the mounting train is capable of taking in at the summit or on the descent will be carried without fresh outlay of engine-power. This may be very important. In the case supposed above of a line whose gradients require in mounting a tractive force double that needed on the level, let it be assumed that the tonnage of raw produce descending is four times that of the manufactured goods ascending; let the engines be capable of taking up twenty wagons weighing five tons, and carrying eight tons each but only one quarter loaded. The gross weight of the mounting train, including engine, would be • Engine 30 tons + wagons 100 tons + load 40 tons = 170 tons; and the tractive force required would, by the supposition, draw 340 tons over the same distance on a level. The descending train being fully loaded would weigh : Engine 30 tons + wagons 100 tons + load 160 tons = 290 tons ; but the tractive force required in descending would be nil. To do the work on the level a tractive force exactly proportional to the gross tonnage is required, or 170 + 290, or making a correction of tea tons each way for the superior lightness of the engine needed : 160 + 280 = 440 tons. On the line with Gradients 170 x 2 = 340 tons. Put in tabular form it stands thus :—

9—D. 2.

Line with Gradients. Line on the Level. Ingine Wagons ioad ... Rising. 30 tons 100" „ 40 „ Descending. 30 tons 100 „ 160 „. Engine Wagons Load ... Power expendedf Q-oing. 20 tons ... 100 „ ... 40 „ ... 160 „ Returning. 20 tons 100 „ 160 „ Power expended* 170 x 2 Nil 280 JJ * Total lower ex; icnded, 34,0. t Total power expended, 440.