THE GROWTH OF THE STEAM-ENGINE. 69 



improvement we may feel assured will rapidly take place, as it is now 

 becoming well understood that care, skill, and intelligence, are absolute- 

 ly essential to economical management, as well as to safety, and that 

 they repay liberally all the expenditure of time and money that is 

 requisite to secure them. It is truer of labor than of anything else in 

 the market that " the best is the cheapest." 



In attempting improvement in the directions that I have indicated, 

 it would be the height of folly to assume that we have reached a limit 

 in any one of them, or that we have even approached an impassable 

 limit. If further progress seems checked by inadequate returns, when 

 efforts are made to advance, in any promising direction, beyond pres- 

 ent practice, it becomes the duty of the engineer to detect the cause 

 of such hinderance, and, having found it, to find a way to remove it, if 

 such removal is not physically impossible. 



A few years since the movement toward the expansive working of 

 high steam was checked by experiments seeming to prove positive dis- 

 advantage to follow advance beyond a certain point. A careful revision 

 of results, however, showed that this was true only with engines built, 

 as was then common, in utter disregard of all the principles which 

 should have been observed in such use of steam, and of the precau- 

 tions necessary to be taken to insure the gain which science has taught 

 us should follow the intelligent use of higher pressures of steam. The 

 obstructions are purely physical and mechanical, and it is for the en- 

 gineer to remove them. 



An analysis of the methods of waste of heat, in the operation of the 

 modern steam-engine, would show that a very large proportion nearly 

 all, in fact is due to the rejection of unutilized heat with the exhaust- 

 steam. In the best engines in general use this loss amounts to from 

 eight-tenths to nine-tenths of the total amount of heat derived from 

 the fuel. Modern steam-engines lose nearly all wasted heat in this 

 way; the losses by conduction and radiation are comparatively small. 

 It is at once evident that the only way in which anv very great addi- 

 tional economy can be secured is to reduce to a minimum the quanti- 

 ty of heat remaining at the opening of the exhaust-valve, and then to 

 retain this rejected heat within the system, so far as is possible, and to 

 thus prevent its waste by escape from the system. The reduction of 

 the great quantity of heat left for rejection at the end of the stroke 

 of the piston can only be effected, to any important degree, by expe- 

 dients which check that internal condensation and reevaporation which, 

 with great expansion, transfer to the condenser, unutilized, an immense 

 amount, often, of the heat supplied. As already stated, these expe- 

 dients are the use of dry steam, the adoption of the steam-jacket and of 

 high engine-speed, and the use of a material for the interior lining of 

 the cylinder which has the least possible conductivity. 



The retention of the heat actually rejected from the cylinder, and 

 its complete utilization by reworking, is practically a matter of diffi- 



