80 
and then that these mountain glaciers were as much a proof 
of heat as of cold, and to produce the vapour to condense 
and form glaciers required as much heat as would raise five 
times the weight of the glaciers of cast iron to its melting 
point.” The heat required to convert water into steam as it 
passes from the sensible into the latent state is a known 
quantity, so also is the amount required to convert ice into 
water ; but that required to melt a pound of ice and evapo- 
rate a pound of water Avould fall far short of melting five 
pounds of cast iron. 
That no mechanical energy is exerted in the conversion of 
water into steam is obvious to our senses, since evaporation 
is the most gentle, imperceptible, as well as the most 
universal action in Nature’s laboratory; and although the 
elasticity of the steam itself exerts mechanical force, equal 
to the atmospheric pressure, chemical force alone is concerned 
in evaporation, and therefore cannot be compared with 
falling bodies, so that the alleged energy and clashing force 
of atoms, in the actions of water cited, are wholly imaginary ; 
nor can philosophy assert any fact relating to mechanical 
action, which cannot be proved by experiment or established 
by plain induction; and in the cases cited, no one can know 
anything about the occult forces and energies of the motions 
of atoms attending the mutations of water. Great lespect 
is due to both of the gentlemen whose essays have invited 
the above strictures ; but the search after the truths of 
science “ should not halt before high names.” 
Mr. Rankine, in offering demonstrations of the dynamical 
origin of heat, allows that heat disappears and becomes latent 
in tcater, in passing from the solid to the liquid state, and 
from this into vapour, as also that the same amount of heat 
is given out and reappears as sensible heat, upon the reversal 
of those changes ; thus in substance admitting the latent heat 
doctrine, whilst denying the materiality of that which does 
so enter into a latent and reappear in a sensible state, and 
