Trrr: trials about t o be described have been nude by the Author lrith one of his central-valve enb' mines. They were planned to determine certain points in connection >$-it11 its economical performance at various speeds and with various steam-pressures; also to obtain figures for comparison with the 1.esults gathered from other types of steam-engine. In the course of the first few trials, many questions arose in connection with initial condensation in the cylinders ; ancl in order, i f possible, to learn something of the effect of surface, range of temperature, ancl speed of rotat,ion in increasing or diminishing this condensation, the original group of trials has been added to considerably. Subsequent trials will include condensing as well as non-condensing tests, trials on the brake, and trials in Connection with the dynamo-111acllincs for driving which the central-valve engine has been used. This Paper deals with the non-condensing trials, and includes trials of the same engine as a simple, a compound, and a tripleexpansive engine. These have been made with steam-pressures varying from 40 lbs. to 170 lbs. per square inch, and at fro111 110 to 420 revolutions per nlinute. The Author is not aware of any trustworthy experiments having been previously made with engines running at so high a speed. The trials at high steam-pressures have also, so far as he knows, been few and isolated. His aim was to show, with some approach t o accuracy, t,he effect of varying steam-pressures and varying ratios of expansion.

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Procccdings.] DISCUSSION ON COMPOUND LOCOXOTIVES. 51 the Author. St p. 21 it was stated that the tank-engines and ~r .Lapage.shunting-engines would have equal cut-offs in both small and large cylinders. Xr. von Borries had the differential cut-off in both forward and backward gear, and it was fitted to the Alsace and Lorraine engine nlentioned in Table I. It had a cut-off in forward gear in about the working notch of 40 per cent. highpressure and 47 low-pressure; full gear 74 per cent. and 58 per cent. : back gear 40 per cent. high-pressure and 44 per cent,. lowpressure ; full gear 75 per cent. high-pressure and 78 per cent.. lowpressure. The engine saved about 18 per cent. of fuel and water.The Author had pointed out that the high-pressure cylinder of the colnpound engine, when only two cylinders were used, should be somewhat larger than the high-pressure cylinder of an ordinary engine. Mr. Lapage was of the same opinion. Judging from what he had been able to observe and gather, from the engines he had sent abroad, there was no doubt that the high-pressure cylinder should be a little larger; but it all depended on the work to be clone and the weight on the driving-wheels. Colnpound engines would haul heavier trains than ordinary engines with the same boiler-power. With regard to the receiver of two-cylinder engines, he thought it was better to have it about l& the capacity of the high-pressure cylinder.AS to the stealn being throttled in the way described, if a relief-valve were placed on the receiver, loaded to about the working-pressure in the receiver, to let it out, he thought it would be rather an advantage for re-starting. Speaking of the. disadvantages of compounding, the Author had pointed out that compound engines had required more oil than ordinary engines. The result referred to might perhaps he ascrihed to the engine being new. I n specifying a compound locomotive, he put only one lubricator on the high-pressure side, and as the steam went over t o the low-pressure side it naturally took up the oil, provided there was no exhaust from the high-pressure cylinder to the atnlosphere ; moreover, the low-pressure cylinder was somewhat clamp and did not need nzuch oil. The machinery should not require nlore oil, as there was less strain on a compound engine. Highpressure steam was stated to be a drawback; this was not essential, for by arranging the cylinders to the required capacity good results were obtained ; but as high-pressure steam could be utilized betber in a compound than in an ordinary engine, it was used when practicable. I n a two-cylinder compound engine, when the high and the low pressure were arranged to start with about equal power, the moving parts of each engine were of the same dimensions, except as regarded the low-pressure piston and slide-valve, E 2 Downloaded by [] on [11/09/16].