These gentlemen begin by an investigation of the expansion of air by heat. The absolute expansion of air from freezing of water to boiling had been previously determined by Gay Lussac and myself to be from 8 to 11 nearly: they however extended the enquiry above and below these points of temperature, namely to those of freezing and boiling mercury. From the temperature of freezing mercury or thereabouts, to that of boiling water, they find the expansion of air to keep pace with that of mercury, as indicated by the common thermometer; but from the boiling point of water to that of mercury, the latter expands somewhat more in a proportion gradually increasing: as by the following Table. TABLE I. +------------------------+-----------------+-----------------------+ | | | Temperature by an | | | | air Thermometer, | |Temperature by Mercurial| Corresponding | corrected for | |Thermometer. |volume of a given| expansion of glass. | | | mass of air. | | |Fahrenheit.| Centigrade.| | Centigrade. | +-----------+------------+-----------------+-----------------------+ | -33° | -36°| 0.8650 | -36.8 | | 32 | 0 | 1.0000 | 0 | | 212 | 100 | 1.3750 | 100 | | 302 | 150 | 1.5576 | 148.70 | | 392 | 200 | 1.7389 | 197.05 | | 482 | 250 | 1.9189 | 245.05 | | 572 | 300 | 2.0976 | 292.70 | | 680 |M. boil 360 | 2.3125 | 350.00 | +-----------+------------+-----------------+-----------------------+ The absolute dilatation of mercury claims their attention. They quote nine authorities for the expansion from freezing to boiling water temperatures; the extremes of these nine are, Casbois ¹/₆₇ of original volume, and mine ¹/₅₀ of the same. They determine it to be ¹/₅₅.₅. By doubling and tripling the elevation of the temperature, they made observations from which are deduced the results of the following Table. The dilatations are for each degree of the thermometer centigrade, to which I have added the corresponding ones for Fahrenheit’s.