203 
by the condensation of gases as mechanical agents. 
tremely small ; and if future experiments should realise the 
views here developed, the mere difference of temperature 
between sunshine and shade, and air and water, or the effects 
of evaporation from a moist surface, will be sufficient to pro- 
duce results, which have hitherto been obtained only by a 
great expenditure of fuel. 
I shall conclude this communication by a few general ob- 
servations arising out of this enquiry. 
There is a simple mode of liquifying the gases, which at 
first view appears paradoxical, namely, by the application of 
heat ; it consists in placing them in one leg of a bent sealed 
tube confined by mercury, and applying heat to ether, or 
alcohol, or water, in the other end. In this manner, by the 
pressure of the vapour of ether I have liquified prussic gas 
and sulphureous acid gas, the only two on which I have 
made experiments ; and these gases in being reproduced 
occasioned cold. 
There can be little doubt that these general facts of the 
condensation of the gases will have many practical applica- 
tions. They offer easy methods of impregnating liquids 
with carbonic acid and other gases, without the necessity of 
common mechanical pressure. 
They afford means of producing great diminutions of tem- 
perature, by the rapidity with which large quantities of 
liquids may be rendered aeriform ; and as compression oc- 
casions similar effects to cold, in preventing the formation of 
elastic substances, there is great reason to believe that it 
may be successfully employed for the preservation of ani- 
mal and vegetable substances for the purposes of food. 
April 1 5, 1823. 
