I *s 2 3 
XXVI. An Account of fome new Experiments on the Production 
of artifical Cold. In a Letter jrom Thomas Beddoes, 
M. D. to Sir Jofeph Banks, Bart. P. R. S. 
Read May io, 1787. 
DEAR SIR, Oxford, May 2, 1787. 
M R. Walker, Apothecary to the RadclifFe Infirmary 
here, has been engaged upwards of a year in a feries 
of experiments on the means of producing artificial cold, feve- 
ralof which feem to me to be very remarkable, and fuch as, con- 
fldering their novelty, and the attention which has lately been 
paid to this fubje£t, I flatter myfelf, will be found to deferve a 
place among the Tranfadtions of the Society over which you 
Mr. Walker, in his firft experiments, found, as Boer- 
haave had done before him, that fal ammoniac, as well 
as nitre, well dried in a crucible, and reduced to a fine powder, 
will produce a greater degree of cold than if they had not re- 
ceived this treatment. But Bof.rhaave, by fal ammoniac, 
lowered the temperature of water only by 28°; whereas Mr. 
Walker obferved his thermometer to fall 32 0 , and when he 
ufed nitre 19 0 . It occurred to him, that the combination of 
thefe fubftances would produce a greater effedt than either fepa- 
rately : and he found that this was really the cafe. A pro- 
pofal for freezing water in fummer, mentioned by Dr. Wat- 
son (Eflays, III. 139-) determined him to attempt the fame 
thing 
