1 90 THE. ADDRESSES, LECTURES, ETC., OF 



and that we had reached another starting-point in applied 

 science commensurate to the one then just accomplished in pure 

 science. 



It was evident, that in order to produce greater results, higher 

 temperatures had to be resorted to, and it was equally evident, that 

 inasmuch as the range of the elastic fluid giving motion to a 

 working piston was necessarily limited, it would not be 

 possible to convert the whole of the heat that had been employed 

 in producing the highly heated elastic medium into onward 

 motion of the piston, and that, therefore, a method had to be devised 

 for storing the residue of the heat contained in the elastic medium 

 after the accomplishment of each stroke of the engine. Such an 

 appliance presented itself ready-made in the regenerator, or heat 

 recuperator, as it might be more appropriately called, a contrivance 

 which had been suggested as far back as 1817 by the Rev. Robert 

 Stirling, of Dundee, and which, was afterwards applied to a heated 

 air engine by his brother, Mr. James Stirling. 



I will not inflict on you a detailed description of the engine 

 resulting from these reflections, nor an account of the innumerable 

 difficulties and disappointments to which they led. Suffice it to say 

 that I obtained economical results sufficient to prove the correctness 

 of the principles upon which I had gone to work, but the complete 

 practical realisation of those principles (involving, as it does, the 

 use of steam or air very highly heated under pressure) is a matter 

 which has yet to be achieved, as the endeavours of James Stirling, 

 Ericsson, and other pioneers in the same field, have not led to any 

 more satisfactory results than my own. 



On the other hand, the steam-engine constructed upon the 

 general principles laid down by James Watt has undergone some 

 important changes ; these consist of improved modes of firing, 

 improved construction of boilers, the introduction of surface con- 

 densation, and such modifications in the construction of the engine 

 itself as enable us to carry into effect the expansive action of 

 steam to a much greater extent than formerly. These improve- 

 ments have been introduced more particularly into the marine- 

 engine, a class of engines which fifteen years ago compared 

 unfavourably as regards economical results with land-engines, 

 particularly with such as were used for pumping water, known as 

 the Cornish engine, and for giving motion to large factories, for 



