SEVERAL MECHANICAL INVENTIONS, 173 



in the public service may admit of the following explana- 

 tion : — On ships of war, the danger from fire^ and the in- 

 convenience of having such a furnace with its apparatus 

 placed on deck in a position for using the steam- gun 

 eflFectually^ were serious objections. Again, the time re- 

 quired for getting up the steam, in cases of sudden en- 

 counter with an enemy, might compel a surrender before 

 a shot could be thrown from, the steam-battery ; and a yet 

 more serious objection to the plan arose from the injury 

 to the tubes (containing the water) from the unequal heat- 

 ing in the furnace. The requisite heat being very intense 

 softened some of the tubes^ so that they gave way, and 

 allowed water to escape into the fire. Although the 

 quantity of water so escaping was too small to cause ex- 

 plosions, yet it could deaden the fire, reduce the supply of 

 steam, and diminish the force of the projectiles, or entirely 

 suspend them if many of the tubes were thus damaged. 

 The leaking tubes could be easily replaced, and the boiler 

 made again effective in a short time, yet '' such pauses for 

 preparation " in the midst of battle must be fatal to the 

 suspended armj wherefore the famous "steam-gun ex- 

 periments " resulted in a loss of the heavy sums expended 

 on them, and produced to the author nothing beyond some 

 transient and barren fame. 



The after interest, however, attached to the plan of 

 using tubular boilers, arose from this scheme serving to 

 suggest the reversed use of the tubes, viz., by employing 

 them as flues for the furnace, to convey the heat through 

 them to the water surrounding them in an outer boiler ; 

 the water thus heated outside instead of inside the tubes 

 by the flame passing through them, could not injure the 

 tubes by outer pressure; nor could the heat, so passing 

 through them, cause any partial injury, as in the former 

 case. 



