e attraction is matter in the
sense in which that term is used in this law. If there be any other
substance in the universe that is not thus subject to gravitation, then
it is improper to call it matter, otherwise the law should read, "Some
particles of matter attract," etc., which will never do.

We are now assured that there is something else in the universe which
has no gravitative property at all, namely, the ether. It was first
imagined in order to account for the phenomena of light, which was
observed to take about eight minutes to come from the sun to the earth.
Then Young applied the wave theory to the explanation of polarization
and other phenomena; and in 1851 Foucault proved experimentally that the
velocity of light was less in water than in air, as it should be if the
wave theory be true, and this has been considered a crucial experiment
which took away the last hope for the corpuscular theory, and
demonstrated the existence of the ether as a space-filling medium
capable of transmitting light-waves known to have a velocity of 186,000
miles per second. It was called the luminiferous ether, to distinguish
it from other ethers which had also been imagined, such as electric
ether for electrical phenomena, magnetic ether for magnetic phenomena,
and so on--as many ethers, in fact, as there were different kinds of
phenomena to be explained.

It was Faraday who put a stop to the invention of ethers, by suggesting
that the so-called luminiferous ether might be the one concerned in all
the different phenomena, and who pointed out that the arrangement of
iron filings about a magnet was indicative of the direction of the
stresses in the ether. This suggestion did not meet the approval of the
mathematical physicists of his day, for it necessitated the abandonment
of the conceptions they had worked with, as well as the terminology
which had been employed, and made it needful to reconstruct all their
work to make it intelligible--a labour which was the more distasteful as
it was forced upon them by one who, although expert enough in
experimentation, was not a mathematician, and who boasted that the most
complicated mathematical work he ever did was to turn the crank of a
calculating machine; who did all his work, formed his conclusions, and
then said--"The work is done; hand it over to the computers."

It has turned out that Faraday's mechanical conceptions were right.
Every one now knows of Maxwell's work, which was to