n of science, chivalry towards foreigners has been a guiding
principle with the Royal Society.

On the more private amenities indulged in by Professor Tait, I do not
consider it necessary to say a word.

********************

XVII. CONTRIBUTIONS TO MOLECULAR PHYSICS.

[Footnote: A discourse delivered at the Royal Institution, March 18,
1864--supplementing, though of prior date, the Rede Lecture on
Radiation.]

HAVING on previous occasions dwelt upon the enormous differences which
exist among gaseous bodies both as regards their power of absorbing
and emitting radiant heat, I have now to consider the effect of a
change of aggregation. When a gas is condensed to a liquid, or a
liquid congealed to a solid, the molecules coalesce, and grapple with
each other by forces which are insensible as long as the gaseous state
is maintained. But, even in the solid and liquid conditions, the
luminiferous aether still surrounds the molecules: hence, if the acts
of radiation and absorption depend on them individually, regardless of
their state of aggregation, the change from the gaseous to the liquid
state ought not materially to affect the radiant and absorbent power.
If, on the contrary, the mutual entanglement of the molecular by the
force of cohesion be of paramount influence, then we may expect that
liquids will exhibit a deportment towards radiant heat altogether
different from that of the vapours from which they are derived.

The first part of an enquiry conducted in 1863-64 was devoted to an
exhaustive examination of this question. Twelve different liquids
were employed, and five different layers of each, varying in thickness
from 0.02 of an inch to 0.27 of an inch. The liquids were enclosed,
not in glass vessels, which would have materially modified the
incident heat, but between plates of transparent rock-salt, which only
slightly affected the radiation. The source of heat throughout these
comparative experiments consisted of a platinum wire, raised to
incandescence by an electric current of unvarying strength. The
quantities of radiant heat absorbed and transmitted by each of the
liquids at the respective thicknesses were first determined. The
vapours of these liquids were subsequently examined, the quantities of
vapour employed being rendered proportional to the quantities of
liquid previously traversed by the radiant heat. The result was that,
for heat from the same source, the order of absorption of liquids