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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].

said he thought the diagrams (Figs. 5, Gand 7, pp. 12, 16 and 19) had not been sufficient,ly explained. I n each case the lines generally represented pumpiug a t a uniform rate. That, of course, was necessary to obtain a line which represented the actual power or force of the spring.In the case of Rickmansworth (Fig. 7), at the lower half, the line coming down showed an increase in the rate of pumping. The pumping was generally carried on at the rate of 15,000 gallons, and then it increased to over 21,000 gallons an hour. The diagram showed the value of increasing the depth and the size of the bore-hole. At Wokingham, the spring continued to fall for a number of hours : in ten hours it had fallen 42 feet, then, on ceasing t o pump, it rose for many hours, but not to its original level. That showed that the water had great difficulty in reaching the borehole, due to the fact that it had to travel a great distance underground. The water was coming on as fast as it could, but it could not get through in consequence of the enormous pressure of the Tertiary beds overhead. The thing t o be sought for in chalkwells was the presence of flints. Wherever there were flints in abundance there was water in abundance, and where there were no flints there was little water. He had often had the idea that the water itself tended to create the flint in chalk, but how far that theory was to be supported by chemists and geologists he did not know. What happened was this :-In flint beds in the Chalk there was a quantity of sand ; and on pumping, that sand gradually worked out, the water dissolving the Chalk and leaving spaces between the flints, through which it could readily travel. In the case of the Leatherhead well, a t t h e bottom there was a continuous bed of flints, hence a vast underground reservoir of water. It was Minutes of the Proceedings of the Institution of Civil Engineers 1887.90:40-90.