No. 216.] 229 



was in common use. These dreadful accidents seem to have originated 

 and kept pace with the use of high pressure steam, or steam of a very 

 high temperature. Steam of thirty pounds or less pressure to the square 

 inch on the piston, is the most elastic, yielding, manageable and free 

 from danger of any known prime mover, and at no time, nor under 

 any circumstances, can such elastic steam exceed the cohesive 

 strength of the weakest part of said boiler, before it burst open. 

 That is to say, the pressure of such elastic steam can at no time 

 exceed the cohesive strength of the weakest part of the boiler in 

 which such steam is generated. 



By a careful examination of the causes of these explosions, and 

 other serious accidents to the working-gear, it is evident that this 

 explosive property or element, be the same whatever it may, is 

 generated by the high temperature of the materials contained in said 

 boiler, and is some other than pure elastic steam. Although steam 

 of great pressure may burst open a cylmdrical boiler laterally in its 

 weakest part, it could never rend the boiler asunder endwise, because 

 the strength of the boilers at the ends is nearly double that of the 

 body of the boiler. Yet in very many of the recorded accidents, the 

 end of the boiler was burst out and thrown several hundred feet. 

 This certainly could only have been effected by an almost unlimited 

 explosive power which is not contained in the properties of elastic 

 steam. 



We can form some accurate idea of the strength of this explosive 

 element, by a careful examination of the strength required for the 

 boilers, working-gear and frames, as now used on steamboats. 



For the first class river steam vessels, their measured strength is 

 at least five hundred pounds to the square inch on the end of the 

 piston, and for sea-going steamers, upwards of seven hundred pounds. 

 This enormous strength has been shown to be necessary by long 

 continued experience. It is evident from the frequent accidents to 

 the working-gear, as well as the boilers, that this great strength is 

 no more than equal to the force which occasionally acts on the piston. 



Although fifty pounds to the square inch on the safety valve for 

 high pressure engines, is perhaps more than their general load, and 

 for low pressure tngiues not one-fifth this load is used, yet the 

 average strength of the boilers and working gear, is required to be 

 made to resist from ten to fifteen times this pressure, and whenever 

 the temperature in the boiler exceeds that required for generating 



