58 Account Mr Edward Nairne’s Process 
viz. that the evaporation from any wet body, and consequently its 
dryness, and the cold arising from evaporation, increase with the 
degree of exhaustion ; and, consequently, that artificial dryness 
and artificial cold may be produced under the [receiver of an 
air-pump. 
In following out the valuable principle of Mr Cavendish, 
Mr Nairne placed several fluids and wet substances under the 
receiver. Three grains of water in a watch-glass lost grains 
by evaporation in 10 minutes ; 100 grains of spirit of wine lost 
9 grains. Every substance which he tried sustained a certain 
loss by evaporation, excepting sulphuric acid^ which always 
gained^ by absorbing the vapour exhaled from the wet part of 
the pump. Having thus ascertained that the exhaustion of 
the air produced a rapid evaporation, and that the sulphuric 
acid absorbed the vapour thus exhaled, Mr Nairne used this 
process for producing dry air in the receiver^ in order to try the 
effect of the passage of the electric fluid through a dry and a 
moist atmosphere. 
I now,” says he, put some sulphuric acid into the recei- 
ver, as a means of trying to make the remaining contents of the 
receiver^ when exhausted^ as much as possible to consist of per- 
manent air only^ unadulterated with vapour^'’ The consequence 
of this was, that the electrical phenomena were exhibited in the 
air which he had dried, and very imperfectly in air which he 
had made damp, by introducing a piece of wet leather, and re- 
moving the sulphuric acid. 
The next step which Mr Nairne takes, is to produce artificial 
cold by the air-pump^ and he gives an account of his experiment 
in the following words: Having lately received from my friend 
Dr Lind some aether prepared by the ingenious Mr Wolfe, I 
was very desirous to try whether I could produce any conside- 
rable degree of cold by the evaporation of aether under a recei- 
ver whilst exhausting. For this purpose, I put the aether into 
a phial, the neck of which was sufficient to admit the ball of a 
thermometer : this being placed on the air-pump, under a re- 
ceiver which had a plate at the top, with a wire passing through 
a collar of leather ; to this wire the thermometer was fixed, by 
which means I could easily dip the ball of the thermometer in- 
to the aether. 
