14. In the Mem. de l'Académie, for 1780 (published in 1784), we have a paper, by Lavoisier, "On certain Fluids which may be obtained in an aeriform State, at a degree of Heat not much higher than the mean Temperature of the Earth." These fluids are sulphuric ether, alcohol, and water. He points out the boiling temperature of these liquids, and shows that at that temperature the vapour of these bodies possesses the elasticity of common air, and is permanent as long as the high temperature continues. He burnt a mixture of vapour of ether and oxygen gas, and showed that during the combustion carbonic acid gas is formed. Lavoisier's notions respecting these vapours, and what hindered the liquids at the boiling temperature from being all converted into vapour were not quite correct. Our opinions respecting steam and vapours in general were first rectified by Mr. Dalton. 15. In the Mem. de l'Académie, for 1780, appeared also the celebrated paper on _heat_, by Lavoisier and Laplace. The object of this paper was to determine the specific heat of various bodies, and to investigate the proposals that had been made by Dr. Irvine for determining the point at which a thermometer would stand, if plunged into a body destitute of heat. This point is usually called the real zero. They begin by describing an instrument which they had contrived to measure the quantity of heat which leaves a body while it is cooling a certain number of degrees. To this instrument they gave the name of _calorimeter_. It consisted of a kind of hollow, surrounded on every side by ice. The hot body was put into the centre. The heat which it gave out while cooling was all expended in melting the ice, which was of the temperature of 32°, and the quantity of heat was proportional to the quantity of ice melted. Hence the quantity of ice melted, while equal weights of hot bodies were cooling a certain number of degrees, gave the direct ratios of the specific heats of each. In this way they obtained the following specific heats: Specific heat. Water 1 Sheet-iron 0·109985 Glass without lead (crystal) 0·1929 Mercury 0·029 Quicklime 0·21689 Mixture of 9 water with 16 lime 0·439116 Sulphuric acid of 1·87058 0·334597 4 sulphuric acid, 3 water 0·603162 4 sulphuric acid, 5 water 0·663102 Nitric acid of 1·29895 0·661391 9⅓ nitric acid, 1 lime 0·61895 1 saltpetre, 8 water 0·8167