82 POLE STEAM-ENGINE. 



" The fire is under the two tubes, and goes under them for 

 45 feet, and then returns again over them, and then up the 

 chimney. Those tubes need no boiler-house, because they are 

 arched over with brick, which keeps them from the weather, 

 and scarcely any engine-house is needed, only just to cover the 

 enginenian. 



" Suppose a 72-inch cylinder (having 4000 inches), at 10 Ibs. 

 to the inch, an 8-feet stroke, working nine strokes per minute 

 (which is more strokes of that length than she will make when 

 loaded to 10 Ibs. to the inch). 



Inches. 



4000 in a 72-inch cylinder, single. 

 10 Ibs. to the inch. 



40000 



8 feet stroke, 



320000 



9 strokes per minute. 



2880000 Ibs. lifted one foot high per minute. 



" Suppose a 33-inch plunger-pole, 10-feet stroke, ten strokes per 

 minute (which is not so fast by three or four strokes per minute 

 as this engine will go, because she will have no heavy beam to 

 return, neither will she have to wait for condensing, like B. and 

 Watt's, which, when loaded, hangs very long on the injection). 



855 square inches in a 33-inch plunger-pole. 

 10 strokes per minute. 



8550 



10 feet stroke. 



85500 



34 Ibs. to the inch, real duty. 



342000 

 256500 



2907000 Ibs. lifted one foot high per minute. 



" I should judge that less than 50 Ibs. to the inch above the 

 atmosphere would be quite enough to do the work of a 72-inch 

 cylinder single, which is but a trifle for those wrought-iron tubes 

 to stand. This engine, everything new, house included, ready 



