720 Transactions of tee American iNSTiruTE. 



the weakened point, and rips or tears from that point in any direc- 

 tion, like a piece of cloth, and the whole expansive power of the 

 heated water and steam is immediately liberated, dealing destruc- 

 tion around. 



In a tube of four inches in diameter, the result is different; its 

 strength to resist internal pressure is from ten to twenty times that 

 of the four-feet shell, and, if burned entirely through at any point, 

 its strength is so great, in proportion to the internal surface exposed 

 to pressure, that no such thing as explosion or tearing open can 

 take place. A mere leak occurs, and the boiler may be used with 

 safety for weeks after the leak occurs, or until the leakage is so 

 great as to prevent the use of the boiler. 



No such thing as the burning out of a tube can take place, unless 

 for the want of water, or its being filled with sediment; in either 

 case, the result of great carelessness or neglect. 



It is demonstrated by experience that this boiler, with proper 

 treatment, will remain free from deposit inside; the water circula 

 tion is very rapid and perfect, and its tubes being straight, and 

 having no large slack-water spaces, the strong current will blow it 

 out very thoroughly and clean. There are no corners for the 

 lodgment of sediment. 



CONVENIENCE FOR EXAMINATION. 



No other boiler yet made presents such perfect accessibility and 

 convenience for examination of the inside; as by loosening the nuts 

 and removing an elbow bend at each end, the inside of any tube 

 can be examined in a few moments; and by taking off two bends at 

 each end, any tube can be quickly removed without disturbing any 

 other portion of the boiler; and in case of injury, a new one can be 

 inserted in its place in an hour, or by putting caps in place of the 

 removed bends, the boiler may be used without a portion of the tubes. 



The outside of the tubes can be thoroughl}^ and easily cleaned 

 with a steam jet or brusli, tlirough several small doors left for this 

 purpose at front and rear ends, and at both sides. This effects an 

 important saving in fuel. 



As before mentioned, but very little soot or ashes will remain 

 upon the tubes, thus greatly reducing the trouble on this account 

 that occm-s in other boilers. 



ENLARGEMENT OR REDUCTION OF SIZE. 



Another important advantage is convenience of enlargement or 

 diminution of size; as a forty-horse power may be cheaply made 



