the Point oj Mercurial Congelation, 
pcred time for afcertaining la this manner to what degree 
quickfilver will contra# by the application of cold. With this 
view this feventh experiment was made : the feveral thermo- 
meters from A to H were as follows, before I began, A 
B 36, C 33, D 24, E 24I, F 33, G 33, H 37. Thole uled 
in the experiment were C, D and H. The firft was to fhew 
the defcent ot the quickfilver ; and the two lad, which were 
fpirit thermometers, were employed to fhew the correfponding 
contractions of the two fubftances, quickfilver and alcohol. After 
above an hour’s attendance on them, I was highly pleafed to 
fee the quickfilver fall to 1 367° below the cypher, efpecially as I 
luppofed, by changing the mixture for a frefn one, I fhould 1 
get it much lower hill. I made another accordingly, and 
removed the inftiuments into it. The quickfilver rofe, as was 
common in changing the mixtures ; but after waiting a confi- 
derable time, without its defcending again, I recollected Profefior 
braun mentioning that his thermometers were always broken 
when below 6oo°. This made me examine mine, and I found the 
bulb was broken and Fallen oft ; and on a diligent fearch in the 
mixture, I could not find either quickfilver or the pieces of 
glafs ; I therefore conclude it had dropped off into the other 
mixture, which unluckily I had thrown away the moment be- 
fore, having occafion to ufe the bafon in decanting the prefent 
mixture : I have no doubt but it broke at the time the quick- 
filver fell fo rapidly. During the courfe of this experiment I 
•put the apparatus (G) into the freezing mixture ; in a minute’s 
time the quickfilver in the inclofed thermometer had iubfided 
into the bulb, and remained fo during the time it continued 
immerfed in the freezing mixture, which was about three 
quarters of an hour; but though the thermometer, which 
made part of the apparatus, fhewed fo great a degree of cold, 
*B b b 2 vet 
