108 REPULSION BY HE.4T. 



and evaporates very slowly. If a silver or platinum 

 capsule, when brought to u bright red heat/ is filled with 

 cold water, the whole mass assumes the spheroidal 

 state, the temperature of the fluid remaining consider- 

 ably below the boiling point, so long as the red heat is 

 maintained. If we allow the vessel to cool below red- 

 ness in the dark, the water then bursts into active 

 ebullition, and is dissipated into vapour with almost ex- 

 plosive violence.* An equal quantity of water being 

 projected into two similar vessels, over the fire, one cold 

 and the other red hot, it will be found that the water in 

 the cold vessel will boil and evaporate long before that 

 in the one which is red hot. 



Another form of this experiment is exceedingly in- 

 structive. If a mass of white hot metal is suddenly 

 plunged into a vessel of cold water, the incandescence is 

 not quenched, the metal shines with a bright white 

 light, and the water is seen to circulate around, but at 

 some distance from the glowing mass, being actually 

 repelled by calorific agency. At length, when the 

 metal cools, the water comes in contact with it, and 

 boils with energy. 



A result similar to this was observed by Perkins, but 

 its correctness most unjustly doubted. Having made an 

 iron shell containing water, and carefully plugged up, 

 white hot, it was found that the steam never exerted 

 sufficient force to burst the vessel, as it was expected it 

 would do. He caused a hole to be drilled into the 

 bottom of the white-hot shell, and he was surprised to 

 find that no water flowed through the orifice, until the 

 iron was considerably cooled, when it issued forth with 

 violence in the form of steam. Here we have the 

 Cagniard de la Tour state first induced, and the calorific 

 repulsion of the spheroidal state supervenes. If water is 

 poured upon an iron sieve, the wires of which are made 

 red hot, it will not percolate ; but on cooling, it runs 

 through rapidly. M. Boutigny, pursuing this curious 



