stals were merely placed in evaporating basins and covered with
paper.

657. The condition of elasticity upon the exterior of the gaseous or
vaporous mass already referred to (626. 627.), must be connected directly
with the action of solid bodies, as nuclei, on vapours, causing
condensation upon them in preference to any condensation in the vapours
themselves; and in the well-known effect of nuclei on solutions a similar
condition may have existence (623.), for an analogy in condition exists
between the parts of a body in solution, and those of a body in the
vaporous or gaseous state. This thought leads us to the consideration of
what are the respective conditions at the surfaces of contact of two
portions of the same substance at the same temperature, one in the solid or
liquid, and the other in the vaporous state; as, for instance, steam and
water. It would seem that the particles of vapour next to the particles of
liquid are in a different relation to the latter to what they would be with
respect to any other liquid or solid substance; as, for instance, mercury
or platina, if they were made to replace the water, i.e. if the view of
independent action which I have taken (626. 627.) as a consequence of
Dalton's principles, be correct. It would also seem that the mutual
relation of similar particles, and the indifference of dissimilar particles
which Dalton has established as a matter of fact amongst gases and vapours,
extends to a certain degree amongst solids and fluids, that is, when they
are in relation by contact with vapours, either of their own substance or
of other bodies. But though I view these points as of great importance with
respect to the relations existing between different substances and their
physical constitution in the solid, liquid, or gaseous state, I have not
sufficiently considered them to venture any strong opinions or statements
here[A].

[A] In reference to this paragraph and also 626, see a correction by
Dr. C. Henry, in his valuable paper on this curious subject.
Philosophical Magazine, 1835. vol. vi. p. 305.--_Dec. 1838._

658. There are numerous well-known cases, in which substances, such as
oxygen and hydrogen, act readily in their _nascent_ state, and produce
chemical changes which they are not able to effect if once they have
assumed the gaseous condition. Such instances are very common at the poles
of the voltaic pile, and are, I think, easily accounted for, if it be
consider