384 SCIENCE IN SHORT CHAPTERS. 



how the critical state of water must be reached, but also 

 its precise temperature; but all this is based on the assump- 

 tion that Watt made no mistake. 



Unfortunately for the simplicity of this theory, Regnault 

 states that his experiments contradict those of Watt, and 

 prove that the latent heat of steam does not diminish just 

 in the same degree as the boiling-point is raised, but that 

 instead of this the diminution of the latent heat progresses 

 30| per cent more slowly than the rise of temperature, so 

 that, instead of the latent heat of steam between boiling- 

 points of 212 and 312 falling from 966-6 to 866-6 it 

 would only fall to 895 -1 or 69 -5 of latent heat for every 

 100 of temperature. 



If this is correct, the temperature at which the latent 

 heat of steam is reduced to zero is much higher than 

 1178 '6, and is, in fact, a continually receding quantity 

 never absolutely reached; but I am not prepared to accept 

 these figures of Regnault as implicitly as is now done in 

 text-books (I was nearly saying "as is now the fashion"), 

 seeing that they are not the actual figures obtained by his 

 experiments, but those of his " empirical formulae" based 

 upon them. His actual experimental figures are very 

 irregular; thus, between steam temperature of 171*6 and 

 183 '2 a difference of 11-6, the experimental difference in 

 the latent heat came out as 4 '7; between steam tempera- 

 ture of 183-2 and 194-8, or 11 -6 again, the latent heat 

 difference is tabulated as 8-0. 



Regnault's experiments were not carried to very high tem- 

 peratures and pressures, and indicate that as these advance 

 the deviation from Watt's law diminishes, and may finally 

 vanish at about 1500 or 1600, where the latent heat 

 would reach zero, and there, according to the above, the 

 critical temperature would be reached. Any additional heat 

 applied after this will have but one function to perform, 

 viz., the ordinary work of increasing the bulk of the heated 

 body without doing anything further in the way of confer- 

 ring upon it any new self-repulsive properties. 



Our notions of solids, liquids, and gases are derived from 

 our experiences of the state of matter here upon this earth. 

 Could we be removed to another planet, they would be cu- 



