Since the publication of the second part of the first volume, (1810) some important essays on the subject of heat have appeared, which have a direct bearing upon some points of the doctrine on that subject inculcated in the said volume. It may be proper to state the results, with such remarks and reflections as have occurred in the consideration of them. In the Annales de Chimie for January 1813, also in the Annals of Philosophy, vol. 2, we find a Memoir on the specific heat of different gases, by M. M. De la Roche and Berard. This exhibits a most laborious and refined series of experiments on this most difficult subject. Great merit seems to be due to them, both for invention and execution. It is unnecessary to describe the particulars of the apparatus and the mode of conducting the experiments, as a description may be found as above referred. It is sufficient to observe that the _calorimeter_ used was a copper cylinder of 3 inches diameter and 6 in length, filled with water, and having a serpentine tube 5 feet in length, running through the interior and opening at both ends on the outside of the vessels. By means of this tube a regular current of any gas of a given temperature (212°) might be passed through the vessel so as to part with its excess of temperature to the water. The quantity of water and the capacity of the vessel for heat were previously determined; and the quantity of heated gas passed through the calorimeter was determinable at any time, as well as the temperature of the water, from the judicious arrangements. It is easy to see that when an apparatus of this kind is at work, the gas will impart heat, more or less according to its capacity, to the water; and that the temperature of the calorimeter will gradually ascend till it arrives at a maximum; that is, till the refrigerating effect of the surrounding atmosphere upon the calorimeter is equal to the heating effect of the current of gas. _The following Table exhibits the results of their experiments._ +----------------+---------------------------------------+ | | Specific Heat | | | Of the same bulk.| Of the same weight.| +----------------+------------------+--------------------+ | Air | 1.0000 | 1.0000 | | Hydrogen | 0.9033 | 12.3401 | | Carbonic Acid | 1.2583 | 0.8280 | | Oxygen | 0.9765 | 0.8848 | | Azote | 1.0000 | 1.0318 | | Nitrous Oxide | 1.3503 | 0.8878 | | Olefiant Gas | 1.5530 | 1.5763 | | Carbonic Oxide | 1.0340 | 1.0805 | | Aqueous Vapour | 1.9600 | 3.1360[24] | +----------------+------------------+--------------------+