On the Rapid Production of Steam. 309 



cylinder would therefore weigh 1582 pounds, exclusive of any al- 

 lowance for rivets and for double thickness at the joints. The 

 weight of the interior shell or flue will be 636 pounds. As the fire 

 is supposed to act on one half of the outer shell, and on the whole of 

 the flue, there would, in case of the heeling of a boat, sufficiently to 



1582 

 throw all the water out of one boiler, be no less than 636+ o =1427 



pounds of iron exposed to the direct action of die fire, and liable to 

 become red hot. By the j^r5^ series of experiments detailed in the 

 paper above alluded to, (page 296,) we see that one pound of at- 

 mospheric steam will be generated from water at 212° by every 

 nine pounds of iron, at a low red heat, in day light 5 consequently, the 



1427 

 metal above supposed would be sufficient to produce „ =fl584 



lbs. of steam from water at 212°, whenever a change of position 

 should favor its influx in sufficient quantity to cover, either by actual 

 submersion, or by violent agitation, the surfaces of the flue and lower 

 arch of the boiler. To calculate the effect of this weight of vapor, 

 we must compare its bulk with the steam-room left in the boiler. 

 The whole interior capacity of the latter is but 82.4 cubic feet ; but 

 in the condition of things now supposed, a small part only of this 

 space is occupied by water. 



The bulk of steam becomes known by comparing its specific 

 gravity with that of the water from which it !S formed. Thus, as- 

 suming the specific gravity of common air, at 60° Fah. to be .00122 

 of that of water at the same temperature, as determined by Biot &; 

 Arago, thq specific gravity of steam compared with air at 60° being 

 .481 to 1, the specific gravity of steam compared with water at that 

 temperature, is .00058682. As 158f lbs. of water at 60° measure 



158.5 . 



—^^-r =2.536 cubic feet, the atmospheric steam, which can be ob- 

 tained from it willbe=2.536-f-.00058682=4321 cubic feet; which, 



4321 362 



divided by the capacity of the boiler, gives "G^=52o^ = 52f, 



nearly, for the number of atmospheres of pressure, supposing the 

 whole to be condensed and confined in the single boiler, within 

 which we have shown that it may be generated. This would give 

 786 lbs. to the square inch. But upon the supposition that while 

 heat continues to be applied to the boiler, from which the water is 

 drained, its connexion with others remains uninterrupted, nearly the 

 usual pressure will be maintained within it. This pressure may be 

 Vol. XX.— No. 2. 40 



