I 395 ] 
XXV. 'Experiments on the Production of artificial Cold, By Mr. 
Richard Walker, Apothecary to the RadclifFe Infirmary at Ox- 
ford. In a Letter to Henry Cavendifh, Efq. F.R.S. and A.S. 
Read June 5, 1788. 
T HE Royal Society having been pleafed to infert, among 
their TranfaCtions for laid year, an account of fome ex- 
periments of mine, relating to the production of artificial 
cold, tranfmitted in a letter from Dr. Beddoes, I am induced 
to mention a few I have made fince. 
Your zealous attention to this fubjeCt, under whofe aufpices 
this, as well as other branches of natural philofophy, hath 
received confiderable improvement, will, I hope, apologize for 
the liberty I have taken in addreffing myfelf to you, efpecially 
lince any new and ufeful faCts I may have afcertained are prin- 
cipally owing to thofe endeavours your excellent Papers have 
incited in me. 
My moft powerful frigorific mixture is the following : 
Of ftrong fuming nitrous acid, diluted with water (rain or 
diddled water is bed) in the proportion of two parts of the 
former to one of the latter, each by weight, well mixed, and 
cooled to the temperature of the air, three parts ; of vitriolated 
natron (Glauber’s fait) four parts; of nitrated ammonia 
(nitrous ammoniac ) three and a half parts, each by weight, 
reduced feparately to fine powder : the powdered vitriolated 
Vpx.. LXXVI 1 I. Ggg natron 
