OF ARTS AND SCIENCES: JANUARY 11, 1870. 143 



" A third remarkable engine is American, both in invention and exe- 

 cution, and forms perhaps the most remarkable feature of the Ameri- 

 can department. It exhibits thoughtful design, ingenious contrivance, 

 refined skill, and admirable execution. It is singularly unlike an 

 English engine. It has four ports on four different parts of the cylinder, 

 two on one side and two on the opposite, each worked by a separate 

 mechanism. These ports are worked by valves, not sliding, like our 

 own, on flat surfaces, but sliding valves on cylindrical surfaces. Close 

 up to the cylinder these valves cut off the steam with scarce a particle 

 of waste room, and so economize to the utmost the high-pressure steam 

 which they admit, and which they use as expansively and as sparingly 

 as possible. The mechanism by which these -valves are moved is to 

 our eye outlandish and extraordinary ; but it is, in truth, refined, ele- 

 gant, most effectual and judicious ; it spares steam to the utmost, but de- 

 velops what it uses to most effect. Then it proportions in an admir- 

 able way the doses of steam it serves out to the continually varying 

 quantity of work the engine has to do. The mechanism of its mechan- 

 ical governor is wonderfully delicate and direct ; the governor is sensi- 

 tive to the most delicate changes of speed, and feels the slightest de- 

 mand upon the engine for more or less work and steady speed. A 

 mechanism as beautiful as the human hand releases or retains its grasp 

 of the feeding valve, and gives a greater or less dose of steam in nice 

 proportion to each varying want. The American engine of Corliss 

 everywhere tells of wise forethought, judicious proportion, sound execu- 

 tion, and exquisite contrivance." 



It appears that within the twenty years since this machinery was per- 

 fected, more than one thousand engines of the kind have been built in the 

 United States, and several hundreds in other countries, giving an aggre- 

 gate of not less than 250,000 horse-power; that, as to economy of fuel, 

 evidence has been afforded to the Rumford Committee, showing a saving 

 over older forms of engine of about one third. As to its other crowning 

 excellence, — uniformity of velocity, — the purchasers of one of the en- 

 gines, now in its eighteenth year of service, certify that, with the power 

 varying from 60 to 3 GO horse-power within a minute, the speed of the 

 engine is not perceptibly affected. 



It is worth noting, that when these medals were voted to you, Mr. 

 Corliss, just a century had passed since James Watt first patented his 

 improvements of the steam-engine. The vast results of these improve- 

 ments — the difference between the engine when "Watt found it and 



