Ne ee a ee a, Sa ee a eee ee eee 
Mr. Webster's experiments respecting dew 99 
necessary to render it a condenser. Otherwise it is difficult to assign 
a‘reason why objects, in themselves equally cold with window glass, 
should not have been equally moist. In the second place, that glass, 
which was sheltered from the full effect of external air by outside 
shutters, was also dry. So striking was this phenomenon, that when 
one half of the external shutter was closed and the other half open, 
the half of the window, which was covered with the shutter, was per- 
fectly dry, and that, which was exposed to the open air, was covered 
with a copious dew. And even when a single fold of the shutter was 
left open the glass exposed was moist, and the remainder dry ; and 
e contra, oe a single fold only 44 was Ch These = icteige 
> . yy 2 ne a SOE eT eae 
‘But eae Sten the uy was overcast with clouds tsi the 
night, no moisture at all was visible on any part of the windows, 
though exposed to the external air... This fact, which appeared two 
or three mornings, but not in succession, as the sky was not clouded 
any two or three nights in succession, certeqponds exactly with the 
phenomenon, which is within every man’s observation, that a cloudy 
night produces no dew. This appears to me one chabepaistsiifeenl: 
and unaccountable phenomena respecting dew ; and the fact now re- 
lated totally overthrows the common solution of the phenomenon. 
The usual idea is, thatin cloudy nights the vapor all ascends, and | 
therefore nore appears adhering to objects at or-near the earth, But 
in the house, Iam speaking of, the dew on the windows in clear 
weather proceeded from the damp walls, or inclosed air. _ Why should 
the same appearance fail in cloudy weather? . The vapor could not 
_ escape from tight rooms and ascend to the clouds; at least, as great 
a:quantity must have been thrown from the walls, and must have float- 
ed in the room in a cloudy night, as inaclear one. I suspect.the 
reason for the phenomens, oth in he hose and in theo air, is, 
