1863.] 229 ['BTiggs. 



working the iron; and that in some way the heat is, by the. many 

 boilers, available when wanted. When working out one furnace, 

 several others are supplying heat, more or less ', and yet each fur- 

 nace, in a day's work, only furnishes what suffices for itself. Con- 

 sequently, the question resolves itself, in this case, into, — how can 

 you so store up heat (or power) that your three or four furnaces 

 should be upon the same ground with three or four out of twelve or 

 twenty ? 



I will consider the store-rooms of power you have. Take your fly- 

 wheel. I assume that to be 18 feet diameter, and to weigh 32,000 

 pounds ; then assuming the diameter of centre of rotary mass to be 

 16 feet, and the number of revolutions per minute, &c., as follows : 

 65 rev. per rain, gives a vel'y per sec, with 16 ft. diam, = 54.5 ft. 

 50 " " " " " " " " = 41.9 ft. 



Now if you consider how far a body must fall to have these velo- 

 cities, (V- = 64.3 h.) 



When V = 54.5 .-. h. =46.2 ft. x 32,000 lbs. = 1,478,400 ft. lbs. 

 V = 41.9 .-. h. = 27.5 ft. X 32,000 lbs. = 880,000 " '' 



Difference, 598,400 " " 



In other words, if the weight of the fly-wheel were permitted to 

 fall from the heights of 46.2 and 27.5 feet, the same velocities would 

 have been attained that 65 and 50 revolutions per minute gives, and 

 the mechanical work given out by slowing the fly-wheel (from 65 to 

 50 revolutions) is 600,000 ft. lbs., (very nearly.) 



Suppose this slowing to take place while rolling a long thin plate, 

 which would be g'^th of a minute in passing the rolls. (That is 



65-1-50 



taking the mean velocity assumed of "^^ = 57i revolutions per 



minute, and taking the rolls at 18 inches diameter or 4 feet 8* inches 

 circumference, then the speed of the periphery of the rolls is 260 

 feet per minute; whence, in g'^th minute a plate 8f feet long would 

 pass the rolls.) Then the fly-wheel will have developed a force 

 represented by 600,000 x 30 ft. lbs. for one minute, or 18,000,000 



lbs. in one minute, equal to ' "^n — =^ ^^^ horse-power, ivhilst 



the force lasts. 



Or, in other words, the fly-wheel will have performed the work 

 which a 540 h. p. engine would have been needed to do. On the 

 other hand, to restore the speed of the fly-wheel in haJf a minute, 

 would only take at the rate of 1,200,000 ft. lbs. per minute, or the 



VOL. IX. — 2e 



