S40 On the Incipient Disengagement of Elastic Fluids, 



same pressure be made to occupy the greater space w r\ it 

 would require a greater quantity of caloric ; and supposing the 

 change from its filling the sphere w r, to its filling the sphere 

 w /, to be effected mechanically by its elasticity, it would be 

 covetous of caloric, and would take it from any substance which 

 touched it. 



This theory will (I conceive) explain all the phenomena, 

 A certain portion of water is converted into steam at the in- 

 ternal bottom of the kettle, which, in its quiescent state, under 

 atmospheric pressure, would occupy the space w /, but by its 

 elasticity or momentum of its particles, at the instant of its 

 conversion, it occupies the space 7V /•', becomes colder than 

 212°, and thus takes heat from the bottom, reducing it below 

 212°, after the supply of heat from the fire has been removed. 

 This reduction of heat can only happen whilst the water is 

 boiling ; after the water has ceased to boil, it soon communi- 

 cates its own heat to the bottom, which explanation accords 

 with the phenomena. 



I cannot prove by experiments, that when gas is liberated 

 from its prison of a fluid, or a ^olid, at the instant of its 

 liberation it goes to occupy more space than it would do 

 solely, by the admitted laws of latent heat ; but I suggest 

 the following consideration, which may make this pro- 

 bable : — If a spring be fixed in a table, be bent towards the 

 right, and afterwards released, it does not merely go back 

 to the place where it will ultimately rest, but by its elastic 

 property, it would go considerably to the left, and would pass 

 its resting-place several times before it be still. May not the 

 spring held down by the finger on the right side represent, or 

 bear an analogy to, gas confined in a fluid or solid ; and may 

 not its proceeding to the left of its resting-place represent its 

 expanded condition immediately after it has gained its free- 

 dom? 



I must now mention another circumstance, which is closely 

 connected with, and comes in aid of, the present subject. 



It has been observed, that on the first removal of any me- 

 tallic vessel from the fire containing boiling water, the ebulli- 

 tion is increased. The solution may be this : — The cold air 

 then surrounding, and coming in contact with, the outside of 



