bis Thermometer with the common mercurial ones. 381. 
Now, as the atmofphere abounds with watery vapour, or 
water diffolved and chemically combined, and muft be parti- 
cularly loaded with it in the neighbourhood of melting ice; 
as the heated body introduced into the funnel muff neceflarily 
convert a portion of the ice or water there into vapour; and 
_ as ice is known to melt as foon as the heat begins to exceed ao: 
or nearly one degree lower than the frzezing poimt of vapour ; 
I think we may from hence deduce, pretty fatisfactorily,. all 
the phenomena I have obferved. For it naturally follows 
from thefe principles, that vapour may freeze where ice is 
melting; that the vapour may congeal even upon. the furface 
of the melting ice itfelf; and that the heat which (agreeably 
to the ingenious theory of Dr. BLack) it emits in freezing, ~ 
may contribute to the further liquefaction of that very ice upon 
which the new congelation is formed. 
Y would further obferve, that the freezing of water is at- 
tended with plentiful evaporation in a clofe as well as an 
open veffel, the vapour in the former condenfing into drops on 
the under fide of the cover, which either continue in the form 
of water, or affume that of ice or a kind of fnow, according» 
to circumftances * ; which evaporation may perhaps be: attri-. 
buted to the heat that was combined with. the water, at this 
moment rapidly making its efcape, and carrying part of the 
aqueous fluid off withit. We are hence furnifhed with a frefh 
and continual fource of vapour as well as of heat; fo that the 
procefles of liquefation and congelation may go on untmter- 
ruptedly together, and even necefiarily accompany one another, 
although, as the freezing muft be in an under proportion to the 
melting, the whole of the ice mutt ultimately be confumed. 
* See Mr. Baron’s paper on this fubject, m, the Memoires of the Academy 
of Sciences at Paris for the year 1753. 
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