FREE CALORIC.

77

contain so great a quantity of caloric, and whoseparticles consequently adhere so slightly together,that they may be converted into vapour withoutany elevation of temperature, merely bv takingoff the weight of the atmosphere. In such liquids,you perceive, it is the pressure of the atmospherealone that connects their particles and keeps themin a liquid state.

CAROLINE.

I do not well understand why the particles ofsuch fluids should be disunited and converted intovapour, without any elevation of temperature, inspite of the attraction of cohesion?

MRS. B.

It is because the quantity of caloric which en-ters into the formation of these fluids is sufficientto overcome their attraction of cohesion. Etheris of this description; it will boil and be convertedinto vapour, at the common temperature of theair, if the pressure of the atmosphere be takenoff.

EMILY.

I thought that ether would evaporate withouteither taking away the pressure of the atmos-phere, or applying heat, and that it was for thatreason so necessary to keep it carefully corked up.