52 THE SCIENTIFIC PAPERS OF 



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 

 Eoyal Institution, by Mr. Grove and Professor Thomson. 



Viewed from the position of the new theory, the heat given out 

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

 effect, amounting to if part of the total heat imparted to the 

 boiler ; and the remaining -^ part was all the heat really converted 

 into mechanical effect. The greater proportion of the lost heat 

 might be utilized by a perfect dynamic engine. A vast field for 

 practical discovery was thus opened out ; but it might yet be 

 asked whether it was worth while to leave our present tried and 

 approved forms of engines, to seek for economy, however great, in 

 a new direction, considering the vast extent of our coal fields. 

 The reply to this objection was, that the coal in its transit from 

 the pit to the furnace acquired a considerable value, which, for 

 this country, might be estimated at 8 per horse-power per annum 

 (taking a consumption of 13| tons of coal, at an average expen- 

 diture of 12 shillings per ton). 



Estimating the total force of the stationary and locomotive 

 engines employed in this country at one million nominal horse- 

 power ; it followed that the total expenditure for steam coal 

 amounted to eight million pounds sterling per annum, of which at 

 least two-thirds might be saved. In other countries, where coal is 

 scarce, the importance of economy becomes still more apparent ; 

 but it is of the highest importance for marine engines, the coals 

 whereof had to be purchased at transatlantic stations, at a cost of 

 several pounds per ton, to which must still be added the indirect 

 cost of its carriage by the steamer itself in place of merchandise. 



These observations, Mr. Siemens thought, might justify him in 

 bringing before the Institution an engine, the result of nearly ten 

 years' experimental researches, which he thought to be the first 

 practical application of the dynamic theory of heat, of which he 

 was proud to call himself an early disciple. Others, more able than 



