[Footnote 24: The result for this last article must be considered more uncertain than any of the previous ones, the experiment being more complicated.] They found the specific heats of equal volumes of air of the pressures 29.2 and 41.7 inches of mercury to be nearly as 1 ∶ 1.2396, differing from the ratio of the pressures or densities, which is 1: 1.358. The above table of the specific heat of the permanent gases (excluding aqueous vapour) was corroborated by the results of another series of experiments in which the principle was varied a little: namely, to find how many cubic inches of each gas at a given temperature were required to raise the temperature of the calorimeter a given number of degrees, and inferring the capacities for heat to be inversely as the quantities of gas employed. The differences in the results were from 1 to 10 per cent., which may be considered small, in experiments of such delicacy. The ratios of the specific heats of several gases being found, it was highly expedient to find the ratio of the specific heat of water, and that of some one gas, as common air. This was effected by passing a small current of hot water through the calorimeter, and comparing the effect of this current with that of the larger one of air, the requisite care being taken to ascertain the quantity of water passing in a given time and its temperature at the ingress. The result of this experiment was that the specific heat of water is to that of common air as 1 ∶ .25 nearly. By two other experiments, varied from the above, results not much differing were obtained, so that the average of the three gave, water to air, as 1 ∶ .2669. Reducing the specific heats of the gases to the standard of water as unity, we have the following Table of the specific heats of equal weights of the respective bodies: Water 1.0000 Air 0.2669 Hydrogen 3.2936 Carbonic Acid 0.2210 Oxygen 0.2361 Azote 0.2754 Nitrous Oxide 0.2369 Olefiant Gas 0.4207 Carbonic Oxide 0.2884 Aqueous Vapour 0.8474 Before we animadvert upon these results, it will be expedient to give an abstract of the not less interesting experiments of Messrs. Dulong and Petit, on heat, as given in the Annales de Chimie and de Physique, vol. 7 and 10.