PRIME-MO VERS. 379 



By these and by other means \ve may hope to improve combustion ; 

 by strict attention to the proportioning of the parts of the boiler we 

 may hope to make the best use of this improved combustion; by 

 higher initial pressure, by greater expansion, and by the general 

 employment of condensation wherever practicable (and by the use of 

 the evaporative condenser there are very few cases in which it is 

 not practicable), we may trust that the steam-engine, even on its 

 present principle, may be rendered more economical than it has ever 

 yet been ; and may give us more than that one-eighth or one-ninth of 

 the total energy residing in the fuel which now alone we get under the 

 very best and most exceptional conditions. A large loss, however, 

 must with steam-engines as we now know them always be incurred. 

 We cannot hope to deal with initial pressures and temperatures corre- 

 sponding with steam of a density equal to that of water ; nor to carry 

 expansion down to the point where ice would be formed in the con- 

 denser. But wonderful as the steam-engine is, worthy as it was and 

 is of Belidor's eulogium (which I read to you), we know it is not the 

 only heat motor ; and we are aware that there are other f6rms of such 

 motors which theoretically at all events promise higher results. 



By improvements in the existing steam-engine, by the invention 

 and development of other heat motors, by the employment of the 

 power of water and of wind, either as principal motors or as auxilia- 

 ries, we may hope for further progress in the machines the subject of 

 my address, " Prime-Movers." 



I have brought before you, of necessity hastily, and therefore (and 

 also on account of my own incapacity for the task) imperfectly, the 

 leading improvements which have been made in Prime-Movers, from 

 the date of the water-wheels of Vitruvius to the best devised steam- 

 engines of our own day. These improvements have been effected by 

 men like Papin, Savery, Newcomen, Watt, Symington, Fulton, 

 Stephenson, and others, who were not mere makers of engines, but 

 were men full of an ardent love of their noble profession, who followed 

 it because of the irresistible attraction it had for them ; followed it 

 from their boyhood to their grave, and in that very following found 

 their great reward. 



These men undoubtedly possessed that combination of science and 

 practice, which combination Dr. Tyndall has told us is necessary if 



