yS On the Freezing of Mercury, &d. 



gaining a proportionate increafe of temperature by the hesf 

 which had pafled into it from the iinmerfed fnow and 

 muriat. 



We now placed a half-pint Wedgewood's cup within a 

 •white ftone-ware jar, infulating it, agreeably to a method 

 fuggefted by our friend Howard, with three corks placed at 

 equal diftances round the veffel, and one at the bottom for 

 the cup to reft upon. This prevented the cup from coming 

 In contact with the jar, which we now placed, with' the cup 

 in it, in the mixture that had feryed for cooling the mate- 

 rials down to + 5° *, adding to the mixture a little more 

 muriat of lime at + 40"' and fnow at + 3 3 . By this means 

 we fecured the advantage of having a cold atmofphere within 

 the jar all round the infulated cup* 



Upon mixing the cooled ingredients, which were now put 

 into the cup, the thermometer, being immerfed in the mix- 

 ture funk to — 50°. Four ounces of pure mercury at -f 40 , 

 in a fmall thin glafs retort, were then introduced into this 

 mixture, which in 15 minutes became perfectly fixed. We 

 obferved that it congealed from the circumference towards 

 the centre, in the fame way as wax or refin fixes in cooling. 



We now broke the retort, and gave tbe mercury feveral 

 blows with the beak of a hammer, which indented, and at 

 laft fractured it : the fracture was fimilar ^o that of zink, but 

 with facets more cubical. Inadvertently taking up a piece 

 of the folid mercury, I experienced a fenfation as if I had 

 received a wound from a rough-edged inftrument. I threw 

 it from me as I would have done a piece of red-hot iron, 

 and was not a little alarmed when I found that the part of 

 my hand which had been in contact with the metal, imme 

 thately after k)ft all fenfation, and became white and dead to 

 the view. 



The mercury in the mean time had become fluid. The 

 time that had pafled from taking it out of the mixture might 



* The fign -f denotes above, and the fign — below o». 



have 



