It was the prevailing opinion; and the difference of gas or vapour was thought to depend on the different manner in which caloric was united with the basis of these two kinds of elastic fluids. In vapour, it was considered as in a latent state; in gas, it was said to be chemically combined. But the late researches of Sir H. Davy have given rise to a new theory respecting gasses; and there is now reason to believe that these bodies owe their permanently elastic state, not solely to caloric, but likewise to the prevalence of either the one or the other of the two electricities.
EMILY.
When you speak, then, of the simple bodies oxygen and nitrogen, you mean to express those substances which are the basis of the two gasses?
MRS. B.
Yes, in strict propriety, for they can properly be called gasses only when brought to an aeriform state.
CAROLINE.
In what proportions are they combined in the atmosphere?
MRS. B.
The oxygen gas constitutes a little more than one-fifth, and the nitrogen gas a little less than four-fifths. When separated, they are found to possess qualities totally different from each other. For oxygen gas is essential both to respiration and combustion, while neither of these processes can be performed in nitrogen gas.
CAROLINE.