Polytechnic Association Proceedings. 715 



utmost caution in the selection of what has in too many instances 

 proved a temble engine of destruction. Yet a slight reduction in 

 price, made by some unprincipled manufacturer, often secures the 

 contract, and an accident, which in many instances should be termed 

 murder, is the result. 



The remark is very common that boiler explosions result only 

 from carelessness; but it is an indisputable fact that the best boilers 

 of the ordinaiy forms, made by the most eminent firms, of carefully 

 selected materials, fitted with the most perfect appliances for safety, 

 and in the hands of sober and competent engineers, are constantly 

 being exploded in all parts of the country. It is also true that 

 the opinions of the highest autliorities difier widely, or totally fail 

 in giving satisfactory explanations of these terrible disasters. 



Taking these two facts into consideration, will not the best prac- 

 tical results be obtained, by first making a boiler of such form and 

 dimensions that it will sustain great unusual pressure without rup- 

 ture; and second, by dividing up the explosive force, so that when 

 the ultimate strength of the pails is exceeded, the rupture may be 

 rendered harmless? 



It will certainly be conceded that no boiler having its entire 

 contents of water and steam in one body, and lialjle to be discharged 

 instantly, carrying death and destruction with them, can be regarded 

 as safe. 



It has been well demonstrated by practical results, that the 

 highest degree of safety can only be found in sectional boilers. 

 This form also ofiers other important advantages, alluded to in 

 another place. 



The safety boiler has no joints in the fire or out of sight. Such 

 joints are very dangerous features of many boilers, causing rapid 

 wearing out; and many explosions, resulting from the weali.ness 

 produced by^corrosion. 



ECONOMY OF FUEL. 



Having discussed the first requisite of a steam boiler, safety, we 

 turn to what is certainly next in importance, viz: economy of fuel. 



It may be unnecessary to mention, that in order to sustain perfect 

 combustion, a large and constant supply of oxygen, or atmospheric 

 air, must be furnished for admixture with the gaseous products 

 from the fuel. It will be conceded that it is impossible to intro- 

 duce sujQ&cient air into the fire-box end of a boiler tube of one and 

 a half or two inches diameter, and say twelve to sixteen feet in 



