r without any elevation of temperature,
merely by taking off the weight of the atmosphere. In such liquids, you
perceive, it is the pressure of the atmosphere alone that connects their
particles, and keeps them in a liquid state.

CAROLINE.

I do not well understand why the particles of such fluids should be
disunited and converted into vapour, without any elevation of
temperature, in spite of the attraction of cohesion.

MRS. B.

It is because the degree of heat at which we usually observe these
fluids is sufficient to overcome their attraction of cohesion. Ether is
of this description; it will boil and be converted into vapour, at the
common temperature of the air, if the pressure of the atmosphere be
taken off.

EMILY.

I thought that ether would evaporate without either the pressure of the
atmosphere being taken away, or heat applied; and that it was for that
reason so necessary to keep it carefully corked up?

MRS. B.

It is true it will evaporate, but without ebullition; what I am now
speaking of is the vaporization of ether, or its conversion into vapour
by boiling. I am going to show you how suddenly the ether in this phial
will be converted into vapour, by means of the air-pump. --Observe with
what rapidity the bubbles ascend, as I take off the pressure of the
atmosphere.

CAROLINE.

It positively boils: how singular to see a liquid boil without heat!

MRS. B.

Now I shall place the phial of ether in this glass, which it nearly
fits, so as to leave only a small space, which I fill with water; and in
this state I put it again under the receiver. (PLATE IV. Fig. 1.)* You
will observe, as I exhaust the air from it, that whilst the ether boils,
the water freezes.

[Footnote *: Two pieces of thin glass tubes, sealed at one end,
might answer this purpose better. The experiment, however, as here
described, is difficult, and requires a very nice apparatus. But
if, instead of phials or tubes, two watch-glasses be used, water
may be frozen almost instantly in the same manner. The two glasses
are placed over one another, with a few drops of water interposed
between them, and the uppermost glass is filled with ether. After
working the pump for a minute or two, the glasses are found to
adhere strongly together, and a thin layer of ice is seen between
them.]

CAROLINE.

It is indeed wonderful to see water freeze in contact with a boiling
fluid!

EMILY.

I am