Artljicial Drying and Freezing by the Aw-Pump. o9 ' 
“ The pump was now worked ; and whilst the receiver was 
exhausting, the ball of the thermometer was often dipped into 
the aether ; and when the degree of exhaustion by the barometer- 
gauge was 65, (which was the utmost in this case that the pump 
would exhaust to), the degree of cold indicated by the fall of 
the quicksilver in the thermometer was 48° below 0° on Fahren- 
heit’s scale ; so that there was a degree of cold produced 103° 
colder than the air in the room where the experiment was made, 
the thermometer in it being at 55° above 0°. The pump was 
kept continually working for half an hour, and the ball of the 
thermometer often dipped into the asther ; but no greater de- 
gree of exhaustion or cold could be produced. The air being 
let into the receiver, the quicksilver in the thermometer rose 
10°, viz. to 38° below 0°. 
Fresh aether being put into the phial to what was remain- 
ing, the thermometer rose to 30° above 0° : the pump Avas then 
worked again constantly for half an hour ; yet by the barome- 
ter-gauge, the degree of exhaustion was now not more than 16^^, 
and the degree of cold produced did not exceed the 11th degree 
beloAV 0°, as appeared by the quicksilver in the thermometer. 
The air being let into the receiver, the remaining aether was ex- 
amined, and there were found several pieces of ice at the bottom 
of the phial, some of them as big as large peas, which, when the 
aether became nearly of the heat of 32°, or freezing point of 
water, were entirely dissolved.” 
The preceding extracts require no commentary. They es- 
tablish in the clearest manner the identity of the frigorific processes 
of Nairne and Leslie ; and, as a proof that this opinion is not 
peculiar to myself, I have much pleasure in stating, what I have 
learned since the above extracts were made, that an eminent 
chemist, who has studied this subject most profoundly, has, for 
some years, in his public course of lectures, felt it to be his duty 
to ascribe to Mr Nairne the discovery of the processes of arti- 
ficial drying and freezing by the air-pump. 
(Z.) 
