S//? WILLIAM SIEMENS, F.R.S. 257 



it'ly the entire suppression of the steam boiler. We are already 

 in possession of gas engines working at moderate expense as com- 

 pared with small steam engines, even when supplied with the 

 comparatively expensive ^s from our town gas mains, and' all 

 1 1 nit, will be required is an extension of the principle of operation 

 already established. It can be easily demonstrated upon purely 

 dynamical principles that a gas engine is capable of realizing a 

 higher proportion of the heat developed in combustion than can 

 ever be expected from a steam engine, for the simple reason that 

 the range of temperature attained in the cylinder of the gas 

 engine greatly exceeds that of the steam engine, and that expan- 

 sive action of the explosive mixture of gas and air can be earned 

 to the utmost limits. According to well-known dynamical laws, 



t if 

 the duty realized in an engine depends upon the value of , 



v 



t being the initial, and t' the final temperature of the expanding 

 gases, stated in absolute degrees of temperature, which in the case 

 of a well-designed gas engine would attain the highest conceivable 

 value. The realization of such a plan would of course involve 

 many important considerations, and may be looked upon as one 

 of those subjects the accomplishment of which may be left for 

 the energy and inventive power of the rising generation of 

 engineers. 



Before leaving this branch of the subject I wish to call attention 

 to a favourite suggestion which I had occasion to make some 

 years ago. It consists in placing gas producers at the bottom of 

 the coal mines themselves, so that instead of having to raise the 

 coal by mechanical power, the combustible gases ascending from 

 the depth of the mine to the surface would acquire by virtue of 

 their low specific gravity such an onward pressure that they could 

 be conducted in tubes to distances of many miles, thus saving the 

 cost of raising and transporting the solid fuel. 



Glasgow with its adjoining coal-fields appears to me a particu- 

 larly favourable locality for putting such a plan to a practical 

 trial, and the well-known enterprise of its inhabitants makes 

 me sanguine of its accomplishment. When thus supplied with 

 gaseous fuel, the town would not only be able to boast of a clear 

 atmosphere, but the streets would be relieved of the most objec- 

 tionable portion of the daily traffic. 



VOL. III. 8 



