, may vary in their
solubility in water from an extreme of high solubility in the case of
hydrogen chloride to the opposite extreme of comparative insolubility
in the case of silver chloride. In this natural series of compounds,
hydrogen chloride is the body nearest akin to water, and silver
chloride the most remote in kinship.
[Footnote 2: _Philosophical Magazine_, August, 1884.]
_3. A Solidified Vortex Ring._
It is in virtue of cohesion that a freely suspended drop of liquid
assumes the spherical form. If such a sphere be dropped on to the
surface of a liquid of higher specific gravity at rest, one obtains
what is called the cohesion figure of the substance of the drop. A
drop of oil, e.g., spreads out on the surface of water until it is a
circular thin film of concentric rings of different degrees of
thickness, each displaying the characteristic colors of thin plates.
The tenuity of the film increases; its cohesion is overcome; lakelets
are formed, and they merge into each other. The disintegrated portions
of the film now thicken, the colors vanish, and only islets of oil
remain. Some liquid drops of the same or higher sp. gr. than water do
not spread out in this fashion, but descend below the surface of the
liquid, and, in descending, assume a ring shape, which gradually
spreads out and breaks up into lesser rings.
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