that they are
inappropriate, and that the ether and its properties cannot be described
in terms applicable to matter. Mathematical considerations derived from
the study of matter have no advantage, and are not likely to lead us to
a knowledge of the ether.

Only a few have perceived the inconsistency of thinking of the two in
the same terms. In his _Grammar of Science_, Prof. Karl Pearson says,
"We find that our sense-impressions of hardness, weight, colour,
temperature, cohesion, and chemical constitution, may all be described
by the aid of the motions of a single medium, which itself is conceived
to have no hardness, weight, colour, temperature, nor indeed elasticity
of the ordinary conceptual type."

None of the properties of the ether are such as one would or could have
predicted if he had had all the knowledge possessed by mankind. Every
phenomenon in it is a surprise to us, because it does not follow the
laws which experience has enabled us to formulate for matter. A
substance which has none of the phenomenal properties of matter, and is
not subject to the known laws of matter, ought not to be called matter.
Ether phenomena and matter phenomena belong to different categories, and
the ends of science will not be conserved by confusing them, as is done
when the same terminology is employed for both.

There are other properties belonging to the ether more wonderful, if
possible, than those already mentioned. Its ability to maintain enormous
stresses of various kinds without the slightest evidence of
interference. There is the gravitational stress, a direct pull between
two masses of matter. Between two molecules it is immeasurably small
even when close together, but the prodigious number of them in a bullet
brings the action into the field of observation, while between such
bodies as the earth and moon or sun, the quantity reaches an astonishing
figure. Thus if the gravitative tension due to the gravitative
attraction of the earth and moon were to be replaced by steel wires
connecting the two bodies to prevent the moon from leaving its orbit,
there would be needed four number ten steel wires to every square inch
upon the earth, and these would be strained nearly to the breaking
point. Yet this stress is not only endured continually by this pliant,
impalpable, transparent medium, but other bodies can move through the
same space apparently as freely as if it were entirely free. In addition
to this, the stress from