43 
Ordinary Meeting-, February 19th, 1861. 
Dr. J. P. Joule, President, in the Chair. 
A Paper was read by J. C. Dyer, Esq., entitled, “ Brief 
Notes on the Freezing-, Thawing, and Evaporation of Water, 
and on the Condensation of Steam, with a View to Enquire 
into the Cause of those Changes.” 
In these Notes the Author merely aimed to place before 
the Society the apparent agency of heat, in the changes that 
water undergoes in passing alternately from one to the other 
of its conditions of ice, water, and steam, and vice versa ; and 
that these mutations are caused, by the taking up and giving 
out of heat, in its sensible or latent state, by the transitions 
reciprocally from one to the other of those states. ' The 
actual amount of the thermometric heat so passing from the 
latent to the sensible state was given, as taken from the 
common tables. On referring to the two ancient theories of 
heat, the one defining it to be, “a material element, sui 
generis , and pervading matter,” &c. ; the other holding it to 
be “ no other than the motions, mechanically excited in the 
minute particles of bodies,” &c it was contended that, by 
this latter or the “ force heat theory,” the melting of ice by 
the action of the sun’s rays could not be explained, since it 
is not by their force, but by the matter of heat that enters 
and becomes latent in the water. The Author then sub- 
mitted that the only solut ion, hitherto offered of the absorption 
of sensible heat, in water and steam, as latent in these, and 
the re-appearance of the same measure of heat, in a sensible 
state, by the acts of condensation and freezing, is to be found 
in the application of Dr. Black’s “ Latent Heat Theory.” 
Considering the force heat theory, as directly conflicting 
with that of latent heat ; they cannot both be sustained, and 
as the latter stands in elementary works as an established law 
in physics, and as it affords a clear explanation of the 
aqueous changes adduced ; it seems incumbent on those who 
Proceedings— Lit. & Phil. Society — No. 10.— Session, 1860-61, 
