66 PHILOSOPHICAL TRANSACTIONS. [aNNO 1736, 



On the Construction of a Quicksilver Thermometer ; also Observations on the 

 Eclipses of Jupiter s Satellites, Anno 1731 and 1732. By M. Jos. Nic. De 

 risle, F.R.S. N°441, p. 221. 



In order to have surer grounds for experiments of natural philosophy in 

 Russia, and that they might be compared with those of other countries, M. 

 De risle applied this winter to the construction of thermometers of mercury, 

 regulated by the expansion of that fluid proportionably to its bulk. This ex- 

 pansion is indeed not very perceptible, considering that Dr. Halley, in the expe- 

 riments he made on it above 40 years since, N° J97 of the Phil. Trans.; found 

 that the said expansion, by the heat of boiling water, was no more than the 

 74th part of the bulk of the mercury. 



M. Amontons also relates, in the Memoirs of the Royal Academy of the 

 year 1704, that this expansion of the mercury is only the 115th part of its 

 bulk from the greatest heat to the greatest cold that is felt at Paris. But M. 

 De risle found in the great cold at Petersburg, on the -t-f Jan. 1732-3, in the 

 morning, that the bulk of the mercury was condensed almost a 50th part of 

 the extent it had in boiling water. The cold on that day, the wind being at 

 east, was one of the severest ever felt there. His new thermometers of mer- 

 cury he had made of a good large size, and in such manner that, having divided 

 in each the whole quantity of contained mercury into 100,000 parts, and having 

 marked the extent of the bulk of that mercury in boiling water, he can at any 

 time see on the divisions of these thermometers, by how many parts the bulk 

 of the mercury is condensed through the present temperature of the air. And 

 though he has made four of these thermometers, which differ very much as to 

 their size, and the quantity of mercury they contain, yet they agree within a 

 very few of these parts. 



As pure mercury is of the same nature every where, and not liable to any 

 alteration from being inclosed in a tube; and as it is probable, that taking it 

 equally purified, it will in different countries be subject to the same expansion, 

 if exposed to the same degree of heat ; for this reason it is probable, these 

 thermometers may very well serve to compare the temperature of dift^erent 

 countries; especially as he found by experience, that these thermometers may 

 be rendered fit enough to mark sensibly the increase or diminution of the bulk 

 of the mercury, within one or two parts out of the 100,000 contained in the 

 whole bulk. This kind of thermometers has also this advantage, that as they 

 mark the proper expansion of the mercury in each temperature of air, they may 

 serve to show every moment the correction to be made in the height of the 

 mercury in simple barometers; which will serve for reducing them to the height 



