

WILLIAM SIEMENS, F.R.S. 327 



the reservoir containing the compressed air and the air-expansion 

 engine was too narrow, and was provided with a throttle valve, 

 there being evidently a vague idea in the mind of the inventor 

 that the air would produce more refrigeration in expanding spon- 

 taneously without doing work than in expanding behind a working 

 piston, an idea which was permissible at that time when the 

 dynamical theory of heat was little understood. That was one of 

 the defects which he pointed out. Another was that the hot or 

 compressed air was not sufficiently cooled before it was expanded, 

 and was not deprived of its moisture. The moisture in air played 

 a considerable part in those machines. At a temperature of C5* 

 Fahr. saturated air contained 1 per cent, of vapour of water, and 

 this had not only to be reduced into the liquid, but also into the 

 solid condition, representing a total absorption of heat to the 

 amount of 1,140 units of heat per Ib. of condensed vapour, which, 

 upon the quantity of air, would represent 15 Fahr. of loss in the 

 effect produced by the expansion. He believed, if these faults 

 had been remedied, the machine would have given satisfactory 

 results. Since that time, a German engineer, Mr. Windhausen, 

 had constructed machines on similar principles, and had, after 

 many fruitless attempts, obtained remarkable results. It was 

 stated, at a meeting in connection with the Vienna Exhibition, 

 that a machine of 1 50 h.-p. produced 30 cwt. of ice per hour, the 

 theoretical result being that that amount ought to be produced by 

 90 h.-p. The cost of producing a hundredweight of ice by this 

 machine was stated to be one shilling a similar result to that 

 obtained in M. Carry's machine. The machine described by the 

 author of the paper was also an air machine a reversed air 

 engine, so to speak and therefore, in a certain sense, analogous 

 to those he had before mentioned. The author did not compress 

 the air, cool it, and then transfer it into a separate cylinder to be 

 re-expanded, but he combined these operations in an engine 

 similar, in every way, to Stirling's air-engine, on a supposition 

 that that was the most perfect air-engine known, and that, in 

 inverting it, he would be likely to obtain the best result of 

 refrigeration. He could not, however, agree in tho opinion that 

 the Stirling engine was a perfect one. It was the first engine 

 containing a regenerator ; but (as he had pointed out in a paper 

 read before the Institution in 1853) it realised at most only from 



