346 Dr. el ag den’s Hljiory of 
and the other confequences deducible from Mr. HUTCHiNs’sex- 
periments have been fo exactly pointed out by Mr. cavendish, 
the real author and firft mover of the whole bufinefs, that 
nothing remains for me but to add a few fupplementary re- 
marks. 
Mod of the appearances which perplexed M. braun in his 
experiments admit of fuch a ready folution from thefe of Mr. 
hutchins, that it would be luperfluous to dwell upon each 
particular ; there is one, however, wliicli muft be mentioned, 
becaufe an erroneous explanation has been given of it by a very 
eminent Sw r edifh philofopher Profeflor braun obferves, 
that by a certain kind of management he could effedt the con- 
gelation of quickfilver with very weak aqua fortis. For this 
purpofe he filled feveral different glades with fnow, into which 
he fucceffively poured the dilute acid of nitre, and immerfed 
his thermometer. The mercury, which would fink only to 
- 148° in the firff glafs, came in the fourth to the term of 
complete congelation. It is no wonder that the profeflor, with 
the ideas he entertained, fhould think this extraordinary ; but 
we now clearly underhand, that the cold in the fir if: glafs was 
fufficient to freeze part of the quickfilver, but did not laff long 
enough to render the whole lolid ; in the fecond glafs a further 
part froze ; in the third dill more ; till at length only fuch a 
quantity was left as the fourth mixture could fully congeal. 
Another phenomenon, of which M. braun gives a very un- 
fatis factory folution, is the finking of the quickfilver in his 
thermometers after they were taken out of the frigorific mix- 
ture. This, I fuppofe, proceeded entirely from its beginning 
to melt in the warmer air, and confequently fubfiding to fill 
up vacuities in the ftem or ball, in the fame manner as hap- 
•* Kongl. Vetenlk, Acad, Handlingar vol, XXXIII, p, 119. 
4 
pened 
