in a short curved piece, k.  The inclination of the block, k, governs the travel of the valve.  The total weight of the engine in working order is:  On the leading wheels, 10 tons 8 cwt.; front drivers, 14 tons 4 cwt.; rear drivers, 13 tons 10 cwt.; total, 37.75 tons.  The tender weighs 25 tons in full working order.  The boiler pressure is 150 lb., and the usual point of cut-off in the high pressure cylinders, when running at speed, is half-stroke, while the pressure of steam admitted to the large cylinder is never to exceed 75 lb. per square inch.  The average consumption of coal between London and Crewe is 26.6 lb. per train mile, or about 8 lb. per mile less than the standard coupled engine.  In an experiment made in October, 1883, one of these engines took the Scotch express from Euston to Carlisle at an average speed, between stations, of 44 miles an hour, the engine, tender, and train weighing 230 tons, with a consumption of 291/2 lb. of coal per mile, and an evaporation of 8.5 lb. of water per pound of fuel.

Mr. Webb’s object, in designing this engine was to secure in the first place a greater economy of fuel, and secondly, to do away with coupling rods, while at the same time obtaining greater adhesion, with the freedom of a single engine.  The cost is much more than an ordinary locomotive, but the saving in fuel is said to be 20 per cent. over the other engines of the North Western Rail way.  These engines run very sweetly, and are said to steam freely, although with only half the usual number of blasts; but from the small size of the high pressure cylinders, they are liable to slip when starting heavy trains, as the low pressure cylinders are not then effective, while the consumption of coal does not seem to show the saving that would have been expected, when compared with ordinary engines doing similar duty on other lines; for instance, the Great Northern single engine takes trains of the same weight with the same consumption of coal and at a somewhat higher speed.  But it must, of course, be borne in mind in making such a comparison, that the fuel used may not be of the same quality.

Mr. Stirling, of the Great Northern, has adopted an entirely different type of engine to those last described.  Holding strongly that single engines are more economical not only in running, but in repairs, and that cylinder power is generally inadequate to the adhesion, he has designed his magnificent well-known class of express engines.  They have single driving wheels 8 ft. in diameter, with a four-wheel bogie in front and a pair of trailing wheels, 4 ft. diameter, behind.  The frames are single, and inside of one solid piece; the cylinders are outside 18 in. diameter and 28 in. stroke; and the valve gear is of the usual shifting link description.  The boiler is of Yorkshire plates, 11 ft. 5 in. long and 4 ft. diameter, and the steam pressure is 140 lb.; while the tractive power per lb. of steam in the cylinders is 94 lb.  The fire-box is of copper, and the roof is stayed to the outer shell by wrought iron radiating stays screwed into both; a sloping mid-feather is placed in the fire-box.