SJR WILLIAM SIEMENS, F.R.S. 105 



consequence was, that the area must be larger to allow a given 

 weight of steam to issue from an orifice, than if water issued under 

 the same pressure, in the proportion of ^477 : / 1, or about 

 21 times the area. But, inasmuch as the quantity of water had 

 to be increased ten -fold, it followed that -^th of 21 times, or 2'1 

 times, ought to be the area of the steam orifice as compared with 

 the orifice in the boiler. This calculation agreed accurately with 

 the proportions it had been found expedient to adopt ; but he was 

 surprised to learn that the same proportions of area were given to 

 the injector, although the conditions of its application, especially 

 as regarded the pressure in the boiler, might be very different. 

 With a pressure of twenty atmospheres, for instance, the density 

 of the steam was 110 times less than that of the water ; therefore, 

 the relative velocity would be as *J 110 : J 1, or as 10'5 : 1, and 

 about double the area of steam would be required to supply the 

 necessary quantity to impel the water forward into the boiler. 



He felt convinced many of the partial failures they had heard of 

 might be due to this, that the injector had been calculated, or 

 determined experimentally, for ordinary high-pressure engines, but 

 if applied to low-pressure, or very high-pressure engines, it failed 

 to work satisfactorily. It could even be shown, that the injector 

 was not applicable at all if the pressure exceeded certain limits. 

 As, with a pressure of twenty atmospheres, the velocity of the steam 

 was only 10 '5 times greater than that of the water, and as the steam 

 must take up about 10 times its own weight of water in order to 

 condense, it would consequently possess only just power sufficient 

 to impart to that amount of water the requisite velocity, when that 

 point would be reached, where the injector would no longer work 

 with water of ordinary temperature. 



The author had referred to the dynamical theory of heat, and 

 had said, that a sudden change in the sheaf took place, when there 

 was an instantaneous conversion of heat into work, a vortex being 

 found in the sheaf, producing this result. Mr. Siemens had been 

 one of the earliest disciples of this new theory of heat ; and in the 

 year 1853,* a paper by him was read at the Institution in which 

 the caloric engines were passed in review by the light of that 

 theory. Taking the case of a pressure of GO Ibs., the force repre- 



* Vide Minutes of Proceedings of the Institution of Civil Engineers, Vol. XII. 

 p. 571, and p. 29, ante. 



