A CENTUKY 8 PK0GKE8S OF THE STEAM ENGINE. 



593 



of tho .same builder, because of the fact that, having no tlvwheel to 

 .steady its speed durino- the piston stroke, it took steam in such a irian- 

 ner as to cause the piston to start with a juuip and to traverse the 

 cylinder .so rapidly as to give comparatively little time for waste by 

 the condensation of th(^ steam upon the cool surfaces of the metallic 

 walls. It maintained its superiority in this respect until other forms 

 oi engine approximated a piston speed approaching that of the older 

 machine, or were provided with arrangements for attaining the same 

 result in reduced wastes by other means. 



Modern engines, other things being equal, improve in efficiency and 

 give increased duty as they increase in speed. Fig. 1 shows what has 

 been the extent and rate of progress in this direction in the case of the 

 marine engine, taken as an example of a type, since the beginning of 

 its Avork and to date; this means, pi'actically, during the nineteenth cen- 

 tury. siiK-e the Avork at earlier 

 dates of Fitch and other invent- 

 ors l)rought forth no practical 

 results. 



John Ste\'ens, in 180-i. and 

 Robert Fulton, in ISOT, were the 

 pioneers in practical employ- 

 ment of the steam engine in 

 marine Avork, though it should 

 not be forgotten tliat John 

 Fitch, in the United States, 

 actually transported passengers 

 for a regular fee on a regularly 

 settled route, (^mj)loy ing scA^eral 

 steamers of small size and very 



moderate speinl, between Philadelphia and Bordentown and Trenton, 

 on the DehiAvare River, scA^eral 3'^ears earlier, between 1787 and 1791. 



In the figure the lowest curve on the diagram represents the progress 

 made in the conservative practice of Watt and his successors and their 

 imitators; the next higher curve shows the advances effected by rivals 

 and more radical constructors from the year 1820 onward; the next in 

 order shows the higher speeds, considered, when Corliss and his con- 

 temporaries introduced them, as dangerously high; while the upper 

 curve exhil)its the limit of radical i)ractice, the danger line, as it Avas 

 tiiought, of the last forty years of the century. Thus it is seen that 

 piston speeds have risen from 200 to 500 feet per minute in marine 

 ])ractice of a conservative kind during the nineteenth century; that 

 what may be to-day called moderate practice has advanced from 300 to 

 600 feet per minute, while high speeds for their dates have increased 

 from 400 feet at about the middl(> of the century to t»00 feet at its 

 close, and, in radical practice, from 500 to 1,200 feet. In «\xceptional 

 SM 99 88 



A. 0. 1800 1820 1810 1860 18«0 1900 



FIG. 1. — MARINE ENGINE PISTON SPEEDS, IS0O-I9OO 



