44(3 PHILOSOPHICAL TRANSACTIONS. [ANNO 1783. 



minutes afterwards the whole was condensed, by the natural cold, into a soft 

 mass very much like tin. While the inner part was still fluid, the frozen surface 

 exhibited a great variety of branched wrinkles; but in general it remained pretty 

 smooth in freezing, as did also a larger quantity of quicksilver which I afterwards 

 exposed to the cold. The congealed mercury was more flexible than lead; but 

 on being bent short it was found more brittle than tin, and when hammered out 

 thin it seemed somewhat granulated. When the hammer had not been perfectly 

 cooled, the quicksilver melted away under it in drops; and the same thing hap- 

 pened when the metal was touched with the finger, by which also the finger was 

 immediately benumbed. In our warm room it thawed on its surface gradually, 

 by drops, like wax on the fire, and did not melt all at once. When the frozen 

 mass was broken to pieces in the cold, the fragments adhered to each other, and 

 to the bowl in which they lay. Though the frost seemed to abate a little toward 

 night, yet the congealed quicksiver remained unaltered, and the experiment with 

 the thermometer could still be repeated. On the 7 th of December I had an 

 opportunity of making the same observations all day; but some hours after sun- 

 set a north-west wind sprung up, which raised the thermometer to — 46°, when 

 the mass of quicksilver began to melt." 



Before this observation of Dr. Pallas's, no person had seen or handled quick- 

 silver frozen by natural cold, so as to submit the fact to the public with compe- 

 tent evidence; but the circumstances here related are so pointed and consistent, 

 that even those who had doubted of M. Braun's experiments were now stag- 

 gered, and began to believe. Indeed, it was scarcely possible to suppose any 

 mistake, when Dr. Pallas had 2 whole days to repeat and vary the experiments at 

 his leisure. But besides removing all doubts on the congelation of quicksilver, 

 these observations tended to show, within certain limits, the degree of cold neces- 

 sary for that effect. It was evident that the freezing point must be somewhere 

 above — 70°, because the thermometer's graduation reached only so low, and yet 

 some part of the mercury always congealed in the tube; and as the solid masses 

 did not begin to melt till the thermometer rose to — 46°, that seemed to be 

 nearly the point at which it passes from a solid to a fluid state, and very possibly 

 was so on this instrument, a difference of several degrees being often found in 

 thermometers so low clown on the scale as — 40°, from inaccuracies in their 

 construction. 



The crystallization of quicksilver also became manifest on this occasion. 

 Hence, when hammered out thin, it showed a granulated texture. The branched 

 wrinkles too, which formed on its surface while it was congealing, could scarcely 

 have proceeded from any other cause, and suggest a general idea of the manner 

 in which it shoots. That quicksilver should crystallize so much more visibly 

 than most other metals, will not appear surprizing, if we consider how little the 



