.

I have observed that steam, immediately issuing from the spout of a
teakettle, is less visible than at a further distance from it; yet it
must be more dense when it first evaporates, than when it begins to
diffuse itself in the air.

MRS. B.

When the steam is first formed, it is so perfectly dissolved by caloric,
as to be invisible. In order however to understand this, it will be
necessary for me to enter into some explanation respecting the nature of
SOLUTION. Solution takes place whenever a body is melted in a fluid. In
this operation the body is reduced to such a minute state of division by
the fluid, as to become invisible in it, and to partake of its fluidity;
but in common solutions this happens without any decomposition, the body
being only divided into its integrant particles by the fluid in which it
is melted.

CAROLINE.

It is then a mode of destroying the attraction of aggregation.

MRS. B.

Undoubtedly. --The two principal solvent fluids are _water_, and
_caloric_. You may have observed that if you melt salt in water, it
totally disappears, and the water remains clear, and transparent as
before; yet though the union of these two bodies appears so perfect, it
is not produced by any chemical combination; both the salt and the water
remain unchanged; and if you were to separate them by evaporating the
latter, you would find the salt in the same state as before.

EMILY.

I suppose that water is a solvent for solid bodies, and caloric for
liquids?

MRS. B.

Liquids of course can only be converted into vapour by caloric. But the
solvent power of this agent is not at all confined to that class of
bodies; a great variety of solid substances are dissolved by heat: thus
metals, which are insoluble in water, can be dissolved by intense heat,
being first fused or converted into a liquid, and then rarefied into an
invisible vapour. Many other bodies, such as salt, gums, &c. yield to
either of these solvents.

CAROLINE.

And that, no doubt, is the reason why hot water will melt them so much
better than cold water?

MRS. B.

It is so. Caloric may, indeed, be considered as having, in every
instance, some share in the solution of a body by water, since water,
however low its temperature may be, always contains more or less
caloric.

EMILY.

Then, perhaps, water owes its solvent power merely to the caloric
contained in it?

MRS. B.

That, probably, would be carrying the speculation too far; I