228 Mr, C, W. Siemens, an a [April 11, 



The steam-engine of Watt was composed of four organic parts, 

 which were pointed out on a working model before the meeting, 

 namely : — 1. The furnace, or chamber of combustion, with its flues 

 and chimney. 2. The boiler, or steam generator. 3. The steam- 

 vessel, or cylinder, wherein the elastic force of the steam is imparted 

 to the piston, or other first moving parts of the machinery. 4. The 

 condenser, where the elastic force of the steam is destroyed by 

 abstracting its latent heat, 'by injection of cold water, or by ex- 

 posure of cooled metallic surfaces.. In the case of high-pressure 

 engines, it would seem that the condenser was suppressed ; but it 

 might be said, that this class of engines makes use of one great 

 common condenser, namely the atmosphere; the separate con- 

 denser possessing only the advantage of relieving the working 

 piston of the opposing atmospheric pressure. The only essential 

 improvement of the steam-engine that has been introduced since the 

 time of Watt consists in working the steam expansively, whereby 

 a considerable economy has been attained ; but it is well known 

 that Watt foresaw the advantages that would be realised in this 

 direction, and was prevented only by insufficiency of the mechanical 

 means at his disposal from realising the same. 



The lofty superstructure proved the soundness of the foundation 

 Watt had laid ; and it would seem hopeless to change the same, 

 unless it could be proved that the very principle regarding the 

 nature of heat, whereon Watt had built, had given way to another 

 more comprehensive principle. The engine of Watt was based 

 upon the material theory of heat that prevailed at his time, and 

 almost to the present day. According to this theory, steam was 

 regarded as a chemical compound of water and the supposed im- 

 ponderable fluid " heat," which possessed amongst others the pro- 

 perty of occupying under atmospheric pressure nearly 1 700 times 

 the bulk of the water contained in it. The Boulton and Watt con- 

 densing engine took the full advantage of this augmentatioh of 

 volume, which effected a proportionate displacement of piston, and 

 the condensation of the steam obviated all resisting pressure toithe 

 piston. 



In the course of the last few years our views of the nature of heat 

 had however undergone a complete change ; and, according to the 

 new " dynamic theory," heat, as well as electricity, light, sound, 

 and chemical action, are regarded as different manifestations of 

 motion between the intimate particles of matter, and can be ex- 

 pressed in equivalent values of palpable motion and dynamic effect. 

 In support of this theory, he (Mr. Siemens) could not do better 

 than refer to the able discourses, recently delivered in the lioyal 

 Institution, by Mr. Grove and Professor Thomson.* 



Viewed from the position of the new theory, the heat given ou^ 

 in the condenser of a steam-engine, represented a loss of mechanical 



* See pp. 152 and 199. 



