1856.] Regenerative Steam-Engir^. 229 



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

 boiler ; and the remaining y'j 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 millions 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 merchan- 

 dise. 



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

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

 years' experimental researclies, 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 

 himself, might probably have arrived sooner at a practically useful 

 result ; but he might claim for himself at least that strong conviction, 

 approaching enthusiasm, which alone could have given him strength 

 to combat successfully the general discouragement and the serious 

 disappointments he had met with. 



The following illustrations, proving the imperishable nature of 

 physical forces and their mutual convertibility, were made use of to 

 indicate more clearly the principles his engine was based upon. 



A weight falling over a pulley, to which it was attached by a 

 string, would impart rotary motion to a fly wheel, fixed upon the 

 same axis with the pulley, and the velocity imparted to the wheel 

 would cause the string to wind itself upon the pulley, till the weight 

 had reached nearly its original elevation. If the friction of the 

 spindle and the resistance ofthe atmosphere could be dispensed with, 

 the weight would be lifted to precisely the same point from whence 

 it fell, before the motion ofthe wheel was arrested. In descending 

 again, it would impart motion to the wheel as before, and this opera- 

 tion of the weight, of alternately falling and rising, could continue 

 ad infinitum. If the string were cut at the instant when the weight 



