EMILY.
Nothing; for it was too well corked for the air to gain admittance, and therefore the upper part of the flask must be a vacuum.
MRS. B.
The water below, therefore, no longer sustains the pressure of the atmosphere, and will consequently boil at a much lower temperature. Thus, you see, though it had lost many degrees of heat, it began boiling again the instant the vacuum was formed above it. The boiling has now ceased, the temperature of the water being still farther reduced; if it had been ether, instead of water, it would have continued boiling much longer, for ether boils, under the usual atmospheric pressure, at a temperature as low as 100 degrees; and in a vacuum it boils at almost any temperature; but water being a more dense fluid, requires a more considerable quantity of caloric to make it evaporate quickly, even when the pressure of the atmosphere is removed.
EMILY.
What proportion of vapour can the atmosphere contain in a state of solution?
MRS. B.
I do not know whether it has been exactly ascertained by experiment; but at any rate this proportion must vary, both according to the temperature and the weight of the atmosphere; for the lower the temperature, and the greater the pressure, the smaller must be the proportion of vapour that the atmosphere can contain.
To conclude the subject of free caloric, I should mention Ignition, by which is meant that emission of light which is produced in bodies at a very high temperature, and which is the effect of accumulated caloric.
EMILY.