Work. 21 



wheels, including two fine specimens of the " Fourneyron " 

 turbine, kindly lent by Mr. Macadam and Mr. Bell, of the Soho 

 Foundry. He showed the crude principle of the steam engine 

 by a long brass tube in which steam was generated, and 

 subsequently condensed, causing a piston to move up and down. 

 The compound and triple expansion types of steam engines, with 

 surface condensers, were explained, and also the theory of the 

 gas engine, by exploding in the same brass tube mixtures of gas 

 and air. The relative efficiencies of steam and gas engines were 

 stated, showing that in recent trials carried out by the Society of 

 Arts a steam engine, working with a boiler pressure of 191 lb. 

 above the atmosphere, and using 1.9 lb. of coals for each 

 indicated horse-power per hour, the efficiency of the engine and 

 boiler only represented 9*6 per cent., showing a loss of over 90 

 per cent, in the theoretical value of thermal units which the coal 

 possessed. Gas engines have a much higher percentage of 

 efficiency, showing a return of 22*8 per cent. It is said that 

 about 50 per cent, of the theoretical power contained in gas is 

 lost in the exhaust of the engine, and about 27 per cent, is wasted 

 in the water jacket surrounding the cylinder. The lecturer 

 indicated that in large engines steam is more economical, owing 

 to the fact that the fuel is less costly, considering the thermal 

 units in coal, but in small ones the balance is in favour of gas. 

 Highly satisfactory results are reported, so far as economy of 

 working is concerned, when Dowson's gas is used. The mode of 

 indicating what power an engine is developing was shown 

 both by diagrams and the friction brake. 



Passing allusion was made to the energy contained in 1 lb. of 

 gunpowder, showing it contains less energy than an equal 

 weight of coal,* and also to the muzzle velocity of heavy cannon 

 balls ; and after expressing his thanks to Mr. Workman, who 

 had kindly lent a beautiful little gas engine, which, with the 

 other class of motors, was at work, and to Messrs. R. Patterson 

 & Sons and Mr. W. T. Coates for various articles lent for th e 

 experiments, the lecturer went on to say that "the sun is the 



♦Experiments go to prove that gunpowder only contains about one-tiuelfth. the energy 

 contained in an equal weight of coal. 



