slowly approach
each other.

Such experiments are very delicate; and with all the precautions taken
by the author, it cannot yet be asserted that he has removed all
possibility of the action of the phenomena of capillarity nor all
possible errors proceeding from extremely slight differences of
temperature. But the attempt is interesting and deserves to be
followed up.

Thus, the hypothesis of the ether does not yet explain all the
phenomena which the considerations relating to matter are of
themselves powerless to interpret. If we wished to represent to
ourselves, by the mechanical properties of a medium filling the whole
of the universe, all luminous, electric, and gravitation phenomena, we
should be led to attribute to this medium very strange and almost
contradictory characteristics; and yet it would be still more
inconceivable that this medium should be double or treble, that there
should be two or three ethers each occupying space as if it were
alone, and interpenetrating it without exercising any action on one
another. We are thus brought, by a close examination of facts, rather
to the idea that the properties of the ether are not wholly reducible
to the rules of ordinary mechanics.

The physicist has therefore not yet succeeded in answering the
question often put to him by the philosopher: "Has the ether really an
objective existence?" However, it is not necessary to know the answer
in order to utilize the ether. In its ideal properties we find the
means of determining the form of equations which are valid, and to the
learned detached from all metaphysical prepossession this is the
essential point.

CHAPTER VII

A CHAPTER IN THE HISTORY OF SCIENCE: WIRELESS TELEGRAPHY

Sec. 1

I have endeavoured in this book to set forth impartially the ideas
dominant at this moment in the domain of physics, and to make known
the facts essential to them. I have had to quote the authors of the
principal discoveries in order to be able to class and, in some sort,
to name these discoveries; but I in no way claim to write even a
summary history of the physics of the day.

I am not unaware that, as has often been said, contemporary history is
the most difficult of all histories to write. A certain step backwards
seems necessary in order to enable us to appreciate correctly the
relative importance of events, and details conceal the full view from
eyes which are too close to them, as the trees prevent us from seeing