844 Transactions of the American Institute. 



sider it probable. I do not suppose lie made so elaborate an investi- 

 gation as has been laid before us to-night ; but I think by a little 

 arithmetical calculation, the proper weight to be put in the piston can 

 be obtained without difficulty. For illustration, taking the cylinder 

 sixteen inches in diameter and thirty-two inches stroke, running at 120 

 revolutions per minute. The diameter of the circle being thirty-two 

 inches, and its circumference eight and one-third feet, the velocity is 

 sixteen two-thirds feet per second, which, for simplicity, we may con- 

 sider exactly equal to one-half g. The velocity varies sensibly as 

 the pressure. A pressure of one pound will give to a mass of one 

 pound a velocity of thirty-two feet in a second ; so that Half a pound 

 pressure will produce the velocity corresponding with the acceleration 

 in a second. If then we have 1,500 pounds in the moving parts, 

 there ought to be 750 pounds pressure on the piston, supposing the 

 acceleration to take place in one second. But, as we have two revolu- 

 tions per second, and as the acceleration takes place in one-quarter of 

 a revolution, it takes place in one-eighth of a second. The velocity 

 varies with the pressure, and, in order to get the required acceleration 

 in one-eighth the time, we must have eight times the pressure, or 

 6,000 pounds ; that is, there must be 6,000 pounds acting on that 

 piston, in order to give it the requisite velocity in mid-position. As 

 the piston has an area of about 200 inches, about thirty pounds mean 

 pressure will be transferred from the first part of the stroke to the 

 latter part of the stroke ; and, in this manner, it is easy to make the 

 calculation with other cylinders, and with a different velocity. 



Mr. C. T. Porter — Eleven or twelve years ago I became interested 

 in the remarkable improvements of Mr. Allen in the valves and 

 valve-gearing of steam-engines. It had long been well settled that 

 the best economy was obtained by working steam expansively, and 

 by variable cut-offs. All the valve-gears adapted to this were some 

 form of the detachable valve-gear of which the Corliss valve-gear is 

 a prominent illustration. There existed no system of working the 

 valves by positive movement. Mr. Allen accomplished this by his 

 adaption of the link motion, and introduced equilibrium valves. At 

 that time I became impressed with the idea that this system of valve- 

 gearing was admirably adapted for the progress of a high-speed engine. 

 I was also impressed with the idea that the day was coming when high 

 speed engines would become a necessity, attaining high speed not 

 merely by making long strokes of nine or ten feet, but combining 

 high speed with a short stroke, giving a rapid rotation ; and this prob- 

 lem I undertook to solve. 



