11     4        44
-- x ------- = ----
19   22_{1/2}  4.28

That is, speaking roughly, 1 lb. of gas gives about ten times as much power as 1 lb. of coal does in a good non-condensing engine.  But at 18s. 8d. a ton we get 10 lb. of coal for 1d.; so that with these figures the cheapness of the coal would just compensate for the efficiency of the gas.  As to the waste heat passing away from the engine being utilized, here the gas-engine has no advantage; and, so far as this is concerned, the gas is about eight times dearer than coal.  The prices of gas and coal vary so much in different places that it is hard to determine in what cases gas or coal will be the dearer fuel, considering this point alone.

But there are other kinds of non-illuminating gases—­such as Wilson’s, Strong’s, and Dowson’s—­which are now coming into use; and at Messrs. Crossley’s works you will have an opportunity of seeing a large engineering factory employing several hundred mechanics, and without a chimney, in which every shaft and tool is driven by gas-engines supplied by Dowson’s gas, and in which the consumption of coal is only 1.2 lb. per indicated horse power.  The greatest economy ever claimed for the steam-engine was a consumption of 1.6 lb.; and this with steam of very high pressure, expanded in three cylinders successively.  Thus in a quarter of a century the gas-engine has beaten in the race the steam-engine; although from Watt’s first idea of improvement, nearly a century and a quarter have elapsed.

As regards the steam-engine, it is the opinion of competent authorities that the limits of temperature between which it works are so restricted, and so much of the heat is expended in producing a change of state from liquid to vapor, that little further improvement can be made.  With respect to gas-engines, the limits of temperature are much further apart.  A change of state is not required, and so very great improvement may still be looked for.  It is not impossible even that some of the younger members of our body may live to see that period foretold by one of the greatest of our civil engineers—­that happy time when boiler explosions will only be matters of history; that period, not a millennium removed by a thousand years, but an era deferred perhaps by only half a dozen decades, when the use of the gas-engine will be universal, and “a steam-engine can be found only in a cabinet of antiquities.”

Discussion.

The President said this was a very delightful paper; and nothing could be finer than Mr. Lane’s description of the conversion of heat into power, and the gradual growth of theory into practical work.

Mr. W. Foulis (Glasgow) agreed that it was admirable; but it required to be read to be thoroughly appreciated.  When members were able to read it, they would find Mr. Lane had given a very clear description of the elementary principles of thermo-dynamics in their relation to the gas-engine and the steam-engine.  There was very little in the paper to raise discussion; but Mr. Lane had made exceedingly clear how the present loss in a gas-engine was occasioned, and had also shown how, in the future development of the engine, the loss might be saved, and the engine rendered more efficient.