142 PROCEEDINGS OF THE AMERICAN ACADEMY 



rence of the regulation by the governor to a system of induction valves 

 of your own invention ; with the advantage of a large saving in fuel, 

 and — what is often more important in manufacturing industry — the 

 maintenance of perfectly uniform motion under varying work. 



Previous to your improvements, the regulation of the power and 

 velocity of the steam-engine was effected by an instrument placed in 

 the steam-pipe, well named the throttle valve; being used to choke off 

 the steam in its passage from the boiler, to reduce more or less its 

 pressure before it was allowed to act within the engine. Avoiding this 

 wasteful process, your engine embodies within itself a principle by 

 which it appropriates the full, direct, and expansive force of the 

 steam, and measures out for itself at each stroke, with the utmost pre- 

 cision, the exact quantity necessary to maintain the power required. 

 In the most approved engines previously used for manufacturing pur- 

 poses, the valves employed were comparatively difficult to operate, 

 too far from the piston, and in other respects unfit for working in con- 

 nection with the governor. Their abandonment, and the substitution 

 of others suitable for the purpose that you had in view, demanded an 

 entire change in the structure of the engine. 



In the reconstruction your mastery of the resources of mechanism 

 is conspicuously shown. You introduced four valves to the cylinder, — 

 two for the induction and two for the eduction of the steam ; and by 

 your device of a wrist-plate you give to each valve a rapid motion in 

 opening and closing, and a slow motion after the closing has been 

 effected, thus securing a perfection in valve-movements never before 

 attained. The special object of these changes, and the gist of your 

 invention, was to place the induction valves under the control of the 

 governor, by which they are operated in opening through a mechanism 

 from which they are released earlier or later in the stroke of the 

 piston, according as more or less power is demanded of the engine, — 

 the governor, with extreme sensibility, determining the point where the 

 supply of steam should be cut off. Thus, at every stroke of the 

 piston, just so much steam is accurately meted out to the cylinder as is 

 needed to maintain uniform velocity, and left to expand there, and by 

 its expansion develop the maximum of propelling force. 



Allow me to read to the Academy a brief account of the Corliss 

 engine, by one of the most eminent of British engineers, Mr. J. Scott 

 Russell, which must needs be free from personal or national pre- 

 possession. It is from one of the official reports on the Paris Universal 

 Exhibition of 1867. 



