THE ADDRESSES, LECTURES, ETC., OF 



numbers to that of the greater given in absolute degrees of tem- 



perature, that the efficiency of the steam is = 



307 + 461 768 



But we must also consider the loss of effect carried away by the 

 heated products of combustion. The temperature of the fire may 

 be taken at 2500, and that of the chimney at 500 Fahr., above 

 the atmospheric temperature, and the ratio of the difference of 



these numbers to the greater gives - = - as the efficiency 



of the furnace, which agrees with that of the best regulated furnaces 

 worked with chimney draught. 



By the multiplication together of these ratios we obtain the com- 



o,- j ii. i.- i m *202 4 808 2 , 



Dined theoretical efficiency of - - x - = - = - (approximately) 



7bo o oo40 I) 



of the steam and furnace worked upon the best known and approved 

 principles. 



Thus it is shown that the best steam-engines now constructed 

 are capable of realising f of the heat generated in the combustion 

 of the fuel under the boiler, whilst the remaining form the margin 

 for future improvement, a large margin, it must be owned, and 

 one that can be dealt with only by increasing the range of tem- 

 peratures, the most perfect engine being one in which the 

 temperature ranges from that produced in combustion, say, 

 3000 Fahr., to the minimum temperature producible in a 

 condenser. 



The production of mechanical work is, however, not the only, 

 nor indeed, the most important employment of fuel ; its largest 

 consumption takes place in the smelting and re-heating of metals 

 and other substances. Here, again, the actual results obtained are 

 very much below those indicated by scientific inquiry. 



Great improvements have, indeed, been effected in blast furnace 

 economy by the introduction of the hot blast by Melson. Yet, if 

 we consider the conversion of iron ore into finished products, such 

 as wrought iron or steel, as a connected process, we find that there 

 remains a very large margin for improvement ; and ultimate 

 economical results can only be looked for, I venture to think, when 

 the several operations now employed are replaced by a direct or 

 single process of conversion. 



In order to heat a pound of iron to the welding point (say, 



