Mr. Webster's experiments respecting dew. rok 
remarked one morning in January, when the weather was very 
cold, the mercury in Fahrenheit standing at 12° below 0, that when I 
first rose, or about sun rise, the windows of my keeping room were 
perfectly free from frost. Soon after, a large fire being kindled, the 
glass of the windows was covered with a fine frost. This phenome- 
non is commonly ascribed to human breath; if this solution is just, 
it proves my supposition ; for the breath issuing from the lungs is 
warmer than the air, and therefore more easily condensed. But this 
- solution cannot be the justone; for the same phenomenon takes place, 
when no person is inthe room. I rather ascribe it to the warmth 
communicated to the air BA the ae Been bhsrons the vapor more 
condensable.s = - 
Every person must nv observed, that in extreme cold weather 
the glass windows of cellars collect frost on the inside. In a series 
of very cold weather in January 1792, I saw an instance of frost thus 
collected ‘more than an inch thick. The vapor in the cellar, being 
peste ‘warm, was of a temperature suitable for condensation. 
~ Thave-a small room adjoining my office, which is kept ‘shuts in 
whackemeré is a window opposite to a-chimney, at the distance 0: 
eight or nine feet. There is no fire kept in this room, nor does any 
person lodge in it ; “yet by micans of a fire in anadjoining room, which 
communicates a degree of warmth to ‘the inclosed air, the vapor be- 
comesseondensable, and in the morning this window is covered with 
dew, when no such phenomenon is visible in rooms not thus warmed. 
~ Every person must have noticed the frost, shooting in the form of 
spicule through the snes —" leading from cellars into upper 
and colder rooms. I ely warm vapor of the cellar, issu- 
et then weather wotteet pa preempt meme 
eli ik te Se 
eerie: f 
