FIGURES UPON ICE, 
160 
than to the face, this theory must be given up ; unless, indeed, 
the top of the head had been forced under the mud, which is 
not very probable. 
I think it very possible that this ice ghost may be put to rest. Proposed ex* 
if any person will place a convex piece of wood, weighted to P enment to 
J 1 1 r . place a piece 
be rather heavier than water, at the bottom of the same pond of wood at the 
next winter, when, perhaps, its figure may become painted on °f the 
the ice in a similar manner to that of the unfortunate person F 
drowned there. 
The fact of the thin covering of snow having been dissolved The absence 
upon the clear ice, and retained upon the rough, may- possibly the^ceofthe 
be owing to the different conducting powers of ice in these figurededuced 
two states. I have frequently observed, that hoar frost Conti- ^con* 
nues longer over hollow drains than in other places, which I ducting pow» 
conceive to be owing to the communication of heat from the er * 
body of the earth being intercepted by the confined air. The 
bubbles, extraneous matters, and confused crystals, of the 
rough ice, may be less capable of conducting caloric, than the 
compact clear ice ; hence, when the temperature of the air 
was below the freezing point many degrees , the snow upon the 
clear ice might be raised nearer to the temperature of 32, or 
that of the water below, than that upon the rough ice, where 
the water from below had less influence. Under these cir- 
cumstances, the sunshine, or other transient warmth, may have 
created a temporary thaw, which has been sufficient to melt 
that thin portion of snow already but little above the freezing 
point, whereas it might not be able, during the same interval of 
time, to raise the other portion of snow from a low tempera” 
tore up to the freezing point, and to dissolve it also. I must 
acknowledge, that it requires a very nice adjustment of all 
these circumstances to have produced the effect described, and 
therefore that less confidence can be placed iu this theory of the 
fact -j but whatever be the true account, it seems probable that 
some unusual combination of circumstances must have taken 
place y and therefore it becomes more justifiable to point out one 
at least of the possible combinations capable- of producing the 
event. 
I remain, Sir, 
Tour obliged and obedient Servant, 
GEORGE CAYLEY. 
P. S. 
