2o 4- Mr. Walker’s Experiments on the 
out, the mercury in it was found congealed, and adhering to 
the glafs. The pan containing the mixed acids, and which 
had been removed whilft the fnow was added to make the 
fecond mixture, was now replaced in it, in order to be cooled ; 
and when the mixture of acids was reduced to the tempera- 
ture of — 34°, fnow previoufiy cooled to— i8° was added, 
keeping the mixture ftirred until the mercurial thermometer 
funk to — 6o° ; its temperature by the fpirit thermometer was 
then found to be — 51 0 . 
The three glaffes containing the mercury to be frozen were 
now immerfed in this mixture, and having been moved about 
In it for a confiderable time, during which the fpirit thermo- 
meter rofe fcarcely one degree, were then feverally taken out 
and examined. 
As the examination of the frozen mercury was more imme- 
diately under the infpedion of Dr. Thomson, I fhall tranfcribe 
here that gentleman’s account of the phenomena. 
66 When the freezing mixture was fuppofed to have pro- 
duced its effeft, the bulb which was completely filled was 
taken out, and broken on a flat ftone by a moderate ftroke or 
two with an iron hammer. This bulb was eleven or twelve 
lines in diameter. 
The folid mercury was feparated into feveral ftiarp and bril- 
liant fragments, feme of which bore handling for a fhort time 
before they returned to a fluid form. One mafs, larger than 
the reft, confiding of nearly one-third of the whole ball, 
afforded the beautiful appearance of flat plates, converging 
towards a center. Each of thefe plates was about a line in 
breadth at the external furface of the ball, becoming nar- 
rower as it (hot inwards. Thefe facets lay in very different 
planes, as is common in the fradture of any cryftallized ball, 
whether 
