EXPERIMENTS on EVAPORATION. 129 
eircumftance leflened my confidence in the refult of the 
laft experiments, itmay be-explained upon the fame prin- 
ciples which explain the others: in the mean time it is 
certain, that when both, razors after being cooled to 0°, 
were moiitened with my breath, and in that fituation ex- 
pofed, one to the open air of 34°, andthe other to the air 
of the ccld veffel, that which was in the veffel lof its 
moifture, while that in the open room appeared to receive 
additional moifture from the air around it. 
it has Jong been known that evaporation continues when 
the air is below 32°; befides the familiar fa@ of drying lih- 
en in freezing weather, Mr. Boyle found that the weight 
of a piece of ice was diminifhed, by expofing it to the 
open air during acold night—Captain James who win- 
tered at Charlton Iflandin Hudfon’s Bay, has related that 
the fnow, in that bitter cold country, often difappears 
without melting. Mr. Wilfon, profeflor of aftronomy at 
Glafgow, obferved that a thin cruft of ice on the cafe of 
his telefcope difappeared while he was making an obfer- 
vation, during an intenfely cold morning: he has related 
this fa&t in the Philofophical Tranfations, and infers from 
it that evaporation continues in very cold weather. 
It therefore is not furprizing that evaporation fhould 
go on in the cold veffel, but from all the circumftances, 
and efpecially from that laft related, refpe@iing the 
razors, I cannot refrain from inferring, that there was 
more evaporation in the cold veflel, than in the air of the 
room, and believe that this fa& may be explained without 
deviating from the true principles of evaporation. 
Water unites with the atmonfphere, or evaporates by 
three procefies, which are (to appearance at leaft,) differ- 
ent from each other. 
1. [fit be expofed to air of its own temperature, or warm- 
er than itfelf, it diminithes infenfibly. 
VOL, Il. aR ae 
