402 
Mr- Walker’s Experiments, See . 
Extract [torn a fecond Eetter from Mr . Walker to Henry 
Cavendifh, Efq- Dated Oxford, May 28, 1788. 
A more intenfe cold may be produced by a folution of falts 
in water in fummer, than can be produced by a mixture of 
fnow and fait in winter. To rain-water fix drachms (by 
weight) I added fix drachms of nitrated ammonia reduced to 
a very fine powder which made the thermometer fink from 
+ 50° (temperature of the materials) to 4 0 , then adding fix 
drachms of mineral alkali very finely powdered the thermo- 
meter funk to - 7 0 , fifty-feven degrees. It is obfervable, that 
in the latter there are two caufes concur in producing the effedt, 
the liquifadtion both of the fnow and fait ; but in the experi- 
ment juft mentioned the liquifadtion of the falts only. 
Vitriolated natron, after it had given out its water of cry- 
flallization byexpofure to the atmofphere, produced no change 
of temperature by folution in the diluted nitrous acid, but 
during folution in water produced heat, as did likewife the mi- 
neral alkali. 
I have fince my laft feen Fahrenheit’s Experiments on the 
freezing of Water, related in Vol. XXXIII. of the Philo- 
fophical Tranfadtions ; but as mine differ in degree I take 
no farther notice of them. 
