THEORY OF THE STEAM ENGINE, CXXXI. 
Tuer PRESENT POSITION or roe THEORY or tHE 
STEAM ENGINE. 
By S. H. Barractoueu, B.E., M.M.E. 
[Abstract of paper read before the Engineering Section of the Royal Society 
of N. 8. Wales, November 18, 1896.] 
Tue purely thermodynamic theory of the steam engine fails to 
take account of the large amount of heat which is stored in the 
metal walls of the cylinder when the steam is admitted, and the 
greater part of which is restored to the steam at the exhaust, 
thus passing through the cylinder without producing any useful 
effect, and also of several other minor losses of heat due to external 
Conduction and radiation. These wastes are gradually being 
investigated, and their mode of variation determined, thus giving 
rise to what has been termed “the experimental theory of the 
steam engine.” 
In dealing with any question of steam engineering there are 
three aspects to be considered, which we may rather roughly but 
satisfactorily term—(1) the financial, (2) the mechanical, (3) the 
Scientific, 
1. The financial side of the question is of course intimately 
connected with the scientific and the mechanical, and is the con- 
trolling factor in designing a steam power plant. The important 
question is not “ What engine will use the least amount of steam 
per H.P. hour”? nor “What boiler will evaporate the greatest 
amount of water per pound of coal”? but it is ‘What complete 
atrangement of the plant will involve the least annual ig iceapnet 
of money”? 
No general principles seem possible with regard to choice of 
type of boiler and engine for maximum commercial efficiency. 
The particular circumstances of any given case have such a pre- 
dominating influence, and vary so widely that it would be impos- 
