67 



under great pressure, nearly the same ^?>Jire is to gunpowder » 

 And this will account for the most destructive cases of boiler 

 explosions ; whilst those of a more harmless nature show that 

 the fractures were small at first, and then gradually extended. 

 He also objected to the term " superheated steam," as being 

 inapplicable to it in any state; because, when steam is in 

 contact with water, it will be of the same temperature as the 

 water; and if heated apart from water, the same laws of 

 expansion by heat apply to steam as to air, and neither can be 

 " superheated," though made very hot. 



Again, steam can never be " mixed up with the water" in 

 a boiler when both are under the same statical pressure, and 

 the steam formed will rise into the chamber, so that the water 

 will always be in contact with the boiler except when steam 

 is drawn off. Still, in rapid escapes, it may drive out water 

 and become entangled therewith, as in many explosions. 



It having been shown that most, if not all, explosions are 

 occasioned by simple steam pressure, acting on the weakest 

 parts at first, and thence extending more or less rapidly, it 

 would seem needless to seek for any other cause or force to 

 account for them ; yet, in some cases, the effects appear to 

 imply a more sudden and violent action, like that of explosive 

 compounds. In such instances, may they not arise from the 

 actual decomposition of the water by heat alone ? Although 

 we have high authority (cited) against this, yet the Autbor 

 held it rash to conclude that water could not be resolved into 

 its constituent gases by direct action of heat from the boiler 

 upon water pressed into contact with the metal plates. It 

 has been proved, long since, that by heat, in the most intense 

 form known to us — that of electricity — water is decomposed 

 and both of its constituent gases are liberated. Therefore, 

 since no evidence has been adduced to show that this does not 

 take place in any water when so confined and heated, the 

 aflfirmative may at least be possible, and seems probable, in 

 some instances, as before named. 



However, he held it desirable that the question should, if 

 possible, be set at rest by experiment; and to this end a 

 method was suggested for putting the matter to a direct test ; 



