452 PHILOSOPHICAL TRANSACTIONS. [ANNO 1733. 



of the bulb, where the whole mass remains, till by its gradual liquefaction it ex- 

 pands again into the tube, and becomes a just measure of the temperature. This 

 agrees exactly with what M. Tornsten observed. In the evening of the 31st the 

 quicksilver congealed in his thermometer, and part of it stuck in the tube at 

 — 54°, but subsided into the vacuity left in the bulb, as soon as it was exposed 

 to heat. When the instrument had been kept in the warm room till the quick- 

 silver re-ascended into the tube, it froze and adhered again in the open air, and 

 the same phenomena were repeated. If M. Tornsten be exact in saying it 

 always became fast at — 54°, the circumstance is curious, and may have de- 

 pended on some particular state of the tube in that part, or on the first shooting 

 of the mercury after it had been cooled to a certain degree below its freezing 

 point. But when the thermometer was carried back into the open air before any 

 of the quicksilver had risen out of the bulb, the effect of the cold could not be 

 to force it up into the tube, and therefore no such appearances were observed as 

 in the former case. With regard to M. Tornsten's remark, that when the whole 

 mass of quicksilver remained in the ball it st ill contracted on the application of 

 heat, the fact is so improbable, and would be perceived with such difficulty, that 

 I have no doubt but he was misled by some prepossession. In like manner on 

 the ] st of January, when the thermometer, having been stationary some hours 

 at — 62°, sunk in the afternoon to — ll6°, it happened unquestionably from 

 the melting and subsiding of a thread of frozen mercury, which had adhered in 

 the tube of the instrument as high as the former degree. None of these effects 

 could be produced when the thermometer had risen to — 31°, because the cold 

 was not then sufficient to congeal the quicksilver. In this easy and simple 

 manner, does our knowledge of the freezing point of mercury enable us to ac- 

 count for phenomena, which were thought so anomalous as to elude every kind 

 of explanation. Even so lately as last year, one of the most eminent philoso- 

 phers in Europe, Professor Wilcke of Stockholm, made a vain attempt to solve 

 the difficulties by a strained application of his doctrine relative to the various spe- 

 cific quantities of heat in bodies, and their different attractions for the matter of 

 heat. It would now be superfluous to add, that the real cold at Brunflo was by 

 no means what the thermometer seemed to indicate, but probably very little ex- 

 ceeded — 39°, or the degree of mercurial congelation, had not M. Tornsten's ob- 

 servations been lately represented, even in this country, as exhibiting an instance 

 of cold actually carried to such a disproportionate and enormous excess. 



Thus is the history of the congelation of quicksilver, both by natural and 

 artificial cold, brought down to the present period. All the facts collected are 

 here delivered : probably however there may be others which have escaped, espe- 

 cially such as are very recent, or have never been published ; but the number al- 

 ready found is greater than was expected on beginning the search. By such a 



