438 PHILOSOPHICAL TRANSACTIONS. [ANNO 1783. 



about 130 ; and Mr. Cavendish finds it amount to 150, and chooses to call the 

 process a generation of heat or production of cold. 



The account of Mr. Hutchins's first success at Hudson's Bay was read before 

 the Royal Society at the commencement of the severest winter that had been 

 known for many years in Europe. Two gentlemen of different countries em- 

 braced this opportunity to attempt the congelation of quicksilver. The first was 

 Dr. Lambert Bicker, secretary to the Batavian Society at Rotterdam, who, on 

 Jan. 28, 1776, at 8 in the morning, made an experiment to try how low he could 

 reduce the thermometer by artificial cold, the temperature of the air being then 

 -J- 2°. He could not bring the mercury lower than — 94 , at which point it 

 stood immoveable ; and on breaking the bulb he saw with certainty that the outer 

 part of the quicksilver had lost its fluidity, and was thickened to the consistence 

 of an amalgam : it fell out of the bulb in little bits, which bore to be flattened by 

 pressure, without running into globules like the inner fluid part. Next day, 

 when the thermometer stood at -f- 8°, he repeated the experiment with all pos- 

 sible exactness, after M. Braun's manner; but could not obtain a greater descent 

 of the mercury than to 80° under O, and did not again break his thermometer. 



The other gentleman who tried the effect of this severe cold in 1776 on mer- 

 cury was Dr. Ant. Fothergill, at Northampton, and the account of his experi- 

 ment may be seen in the Philos. Trans, for that year. His frigorific mixture ap- 

 pears to have been made with the vitriolic acid ; and the natural cold of the air at 

 Northampton that day, the 30th of January, was + Q°. It is scarcely possible 

 to determine how far he succeeded. The quicksilver of his thermometer sunk 

 into the bulb, and it, as well as some in a phial, contracted what Dr. Fothergill 

 calls a film on the top ; but unless the scale of his instrument went below — 40°, 

 or some solid crystals were formed, such as M. Braun and others observed at the 

 commencement of congelation, nothing can be collected with certainty from this 

 experiment. 



Dr. B. next notices some attempts made at Petersburg to freeze pure quick- 

 silver by Dr. Mat. Guthrie, F.R.S. physician to the Cadet Corps of nobles there. 

 From his experiments Dr. G. infers that that metal, when quite pure, never has 

 been nor can be congealed : but the errors he seemed to have fallen into are here 

 refuted by Dr. Blagden. He further adds also, possibly the point of congelation 

 may not be exactly the same in all quicksilver under all circumstances. Foreign 

 admixtures may occasion a difference in this respect ; and it does not follow, that 

 the effect of such, in certain proportions, must necessarily be to make the mer- 

 cury congeal sooner, since, in the case of the fusible metal, the melting point of 

 tin is brought lower by the addition of 2 metallic substances, both of which sepa- 

 rately require a stronger heat than it for their fusion. But as quicksilver bears to 



