e
scientific point of view.

So far as concerns the liquid and gaseous states particularly, the
already antiquated researches of Andrews confirmed the ideas of
Cagniard de la Tour and established the continuity of the two states.
A group of physical studies has thus been constituted on what may be
called the statics of fluids, in which we examine the relations
existing between the pressure, the volume, and the temperature of
bodies, and in which are comprised, under the term fluid, gases as
well as liquids.

These researches deserve attention by their interest and the
generality of the results to which they have led. They also give a
remarkable example of the happy effects which may be obtained by the
combined employment of the various methods of investigation used in
exploring the domain of nature. Thermodynamics has, in fact, allowed
us to obtain numerical relations between the various coefficients, and
atomic hypotheses have led to the establishment of one capital
relation, the characteristic equation of fluids; while, on the other
hand, experiment in which the progress made in the art of measurement
has been utilized, has furnished the most valuable information on all
the laws of compressibility and dilatation.

The classical work of Andrews was not very wide. Andrews did not go
much beyond pressures close to the normal and ordinary temperatures.
Of late years several very interesting and peculiar cases have been
examined by MM. Cailletet, Mathias, Batelli, Leduc, P. Chappuis, and
other physicists. Sir W. Ramsay and Mr S. Young have made known the
isothermal diagrams[6] of a certain number of liquid bodies at the
ordinary temperature. They have thus been able, while keeping to
somewhat restricted limits of temperature and pressure, to touch upon
the most important questions, since they found themselves in the
region of the saturation curve and of the critical point.

[Footnote 6: By isothermal diagram is meant the pattern or complex
formed when the isothermal lines are arranged in curves of which the
pressure is the ordinate and the volume the abscissa.--ED.]

But the most complete and systematic body of researches is due to M.
Amagat, who undertook the study of a certain number of bodies, some
liquid and some gaseous, extending the scope of his experiments so as
to embrace the different phases of the phenomena and to compare
together, not only the results relating to the same bodies, but also
those concernin