Royal Society of Edinburgh . 105 
gradually absorbs latent heat from a point very sensibly lower than 
the zero of the centigrade scale. 
“ I. This explains the permanent lower temperature of the interior 
of ice. 
Ice 
“ Let AB be the surface of a block of ice contained in water at what 
is called a freezing temperature. That temperature is marked by 
the level of the line QP above some arbitrary zero. LM is, in like 
manner, the permanent but somewhat lower temperature possessed 
by the interior of the ice. The space, partly water, partly ice, or 
partaking of the nature of each, MNOP, has a temperature which 
varies from point to point, the portion NO corresponding to what 
may be called the physical surface of the ice between AB and ab, 
which is “ plastic ice,” or “ viscid water,” having the most rapid 
variation of local temperature. 
“ II. Such a state of temperature, though it is in one sense per- 
manent, is so by compensation of effects. Bodies of different tem- 
peratures cannot continue so without interaction. The water must 
give off heat to the ice, but it spends it in an insignificant thaw at 
the surface, which therefore wastes even though the water be what is 
called ice cold , or having the temperature of a body of water inclosed 
in a cavity of ice.* 
“ This waste has yet to be proved ; but I have little doubt of it ; 
and it is confirmed by the wasting action of superficial streams on 
the ice of glaciers, though other circumstances may also contribute 
to this effect. 
“ III. The theory explains “ regelation.” For let a second plane 
surface of ice A'B' be brought up to nearly physical contact with 
“ * I incline to think that water, in these circumstances, may, though sur- 
rounded by ice, have a fixed temperature somewhat higher than what is called 
32°. But I have not yet had an opportunity of verifying the conjecture. 
“ [My idea is that the invasion of cold from the surrounding ice is spent in 
producing a very gradual " regelation” in the water which touches the ice, 
leaving the interior water in possession of its full dose of latent heat, and also 
