['*72 ] 
the fnow, and its mixing with the nitrous acid. For 
as the production of cold depends folely upon the 
folution and mixture, it cannot happen, that this 
mafs, which conftitutes a fluid of a hard kind, fhould 
run into a folid confidence, fo long as the folution 
and mixture continue. 
And now, Gentlemen, it requires no finall (hare 
of your indulgence, to pardon my having extended 
this account fo far : but I have to plead in my ex- 
cufe, that the fubjedt of this work is intirely new, and 
replete with a vail variety of curious faCts ; all which 
exactly fall in with our excellent inftitution. For who, 
before Mr. Braun’s difcovery, would have ventured 
to affirm mercury to be a malleable metal ? who, 
that fo intenfe a degree of cold could be produced 
by any means ? who, that the effcCts of pouring 
nitrous acid upon fnow, fhould fo far exceed thofe, 
which refult from mixing it with ice ; when fnow 
and ice are produced from the fame fubflance, and 
leem to differ only in their configuration ? As Mr. 
Braun’s work is in very few hands, I had reafon to 
hope, that you would not be difpleafed to be in- 
formed, in a degree fomewhat circumftantial, of 
thefe very extraordinary faCts. 
I am, 
With the moft profound refpeCt, 
Gentlemen, 
Your mofl obedient, 
humble fervant, 
/prii 18, 1761. W. Watfon. 
XXXII. Ob- 
