58 ANNUAL OF SCIENTIFIC DISCOVERY. 



aneighth of a pint in the smaller one. It is clear that this pressure 

 could never have been approached, as the light, flat-sided copper 

 boilers did not bulge in the least, while the rush of steam from the 

 outlet never appeared more than could be taken off by an ordi- 

 nary safety-valve. 



The foregoing experiments prove most conclusively the impos- 

 sibility of exploding a red-hot boiler by the sudden injection of a 

 stream of cold water. Every endeavor was made to succeed, and 

 everything that glowing red-hot plates and cold water could do 

 under the circumstances was done. Indeed, the test was much 

 more severe than could occur in ordinary work, either in a house- 

 hold boiler or a boiler employed for engine power. 



To meet the objections of those who would say that, inasmuch 

 as steam-power boilers are ordinarily constructed of wrought-iron 

 plates, with seams of rivets around and along them, they were 

 not fairly represented in these experiments, an ordinary wrought- 

 iron boiler, submitted to a similar test, some years before, gave 

 the following result. The boiler was 25 feet long, and 6 feet in 

 diameter, the safety-valve loaded to CO pounds per square inch, 

 and the empty boiler was then made red-hot, the feed suddenly 

 let in, and the boiler filled up. The only result was a sudden con- 

 traction of the overheated iron, which caused the water to pour 

 out in streams at every seam and rivet as far up as the fire-mark 

 extended. The metallic plates of a steam boiler are not capable 

 of containing sufficient heat to change a very large quantity of 

 water into steam. The total quantity of heat which would raise 

 the temperature of 100 weight of iron through 1 degree would 

 impart the same additional temperature to only 12 pounds of 

 water ; the quantity of heat which would raise the temperature 

 of 100 weight of copper through 1 degree would raise that 

 of 10| pounds of water to the same extent. It is clear, then, both 

 theoretically and practically, that overheating, with the sudden 

 injection of water on red-hot plates, is not the cause of violent 

 boiler explosions. Meek. Mag. May, 1867. 



EXPLOSION OF STEAM BOILERS. 



Overheating cannot be assumed as the general cause of steam- 

 boiler explosions, as these have taken place when there has 

 been an ample supply of water; neither can the sudden pouring 

 of feed water upon red-hot plates account for them ; the electrical 

 hypothesis, in a boiler in direct communication with the earth, is 

 perfectly untenable ; and the decomposition of water is equally 

 unsatisfactory ; the percussive force of steam alone is incapable 

 of producing the destruction attending most steam-boiler explo- 

 sions. 



According to Mr. Zerah Colburn, the following are the suc- 

 cessive steps of a boiler explosion, the action being, however, 

 practically instantaneous: 1. The rupture, under hardly if any 

 more than the ordinary working pressure, of a defective portion 

 of the shell of the boiler, not much if at all below the water-line, 

 from original unsound ness of the iron, bad riveting, corrosion or 



