[Illustration:  FIG. 7.—­MIDLAND RAILWAY.]

The Midland Railway route to the North is distinguished by the heavy nature of its gradients; between Settle and Carlisle, running through the Cumberland hills, attaining a height of 1,170 ft. above sea level, the highest point of any express route in the kingdom; and to work heavy fast traffic over such a line necessitates the employment of coupled engines.  The standard express locomotive of this company has inside cylinders 18 in. in diameter and 26 in. stroke.  The coupled wheels are 6 ft. 9 in. diameter, and the leading wheels 4 ft. 3 in., the total wheel base being 16 ft. 6 in., and the tractive force 104 lb. for each lb. of mean cylinder pressure.  The boiler is of best Yorkshire iron, 10 ft. 4 in. long and 4 ft. 1 in. diameter.  The grate area is 17.5 square feet, and the heating surface is, in the tubes, 1,096; fire-box, 110; total, 1,206.  There are double frames to give outside bearings to the leading axle, as in the Great Western engine, and the engine is fitted with a steam brake.  The weight in full working order is—­leading wheels, 12 tons 2 cwt.; driving wheels, 15 tons; trailing wheels, 11 tons 6 cwt.; total, 38 tons 8 cwt.  The tender weighs 26 tons 2 cwt., and holds 3,300 gallons of water and 5 tons of coal.  Latterly a fine type of bogie express engine has been introduced, with inside cylinders 18 in. diameter and 26 in. stroke, and four coupled driving wheels 7 ft. diameter.  The total wheel base to the center of the bogie pin is 18 ft. 6 in.  The grate area is 17.5 square feet, and the heating surface is, in tubes, 1,203 square feet, and fire-box, 110; total, 1,313; and the engine weighs 42 tons in working order.  These engines take fourteen coaches, or a gross load of 222 tons, at 50 miles an hour over gradients of 1 in 120 to 1 in 130, with a consumption of 28 lb. of coal per mile.  The London, Chatham, and Dover Company has also some fine engines of a similar type.  They have inside cylinders 171/2 in. diameter and 26 in. stroke; the coupled wheels are 6 ft. 6 in. diameter, and the bogie wheels 3 ft. 6 in., the wheel base to the center of the bogie pin being 18 ft. 2 in.  The boiler is 10 ft. 2 in. long and 4 ft. 2 in. diameter, the grate area is 16.3 square feet, and the heating surface is, in the tubes, 962 square feet; fire-box, 107 square feet; total, 1,069.  The boiler pressure is 140 lb., and the tractive force per lb. of steam in the cylinder 102 lb.  The weight in full working order is, on the bogie wheels, 15 tons 10 cwt.; driving wheels, 13 tons 10 cwt.; trailing wheels, 13 tons; total, 42 tons.