it diffuse itself. The rate of movement of
the various particles is varied, by reason of the encounters which each
particle undergoes from time to time. Through experiments made by Joule,
he arrived at the conclusion that particles of hydrogen attained a
velocity of 6055 feet per second at 0 deg. C., which is a velocity much
greater than that of a cannon-ball. In spite of the enormous velocity
with which a particle of hydrogen would move, there are such a large
number of particles in a single cubic inch of space, that no one
particle has an absolutely free path from the one side of the enclosed
space to the other. To this constant movement of the individual
particles is due the elasticity or pressure of gases. The outward
pressure which they exert on any body which encloses the gas is caused
by the total effect of the impact of the particles, and is proportional
to the sum of their masses multiplied into the square of their
velocities. If we halve the enclosed space, then we should double the
number of impacts in a given time, so that the number of impacts is
inversely as the volume of the gas. This is equivalent to the statement,
that the pressure of a gas varies inversely as its volume, which is
Boyle and Marriotte's Law.

ART. 37. _Matter is Gravitative._--If there is one property which is
essentially characteristic to all matter, it is that all matter is
gravitative. To this rule there is no exception, as the universal Law of
Attraction states that "every particle of matter attracts every other
particle." Thus, wherever in the whole universe there is a particle of
matter of any kind or sort, whether such matter be solid, liquid, or
gaseous, there the force of attraction will be exerted with a force
proportionate to the mass of the particle, and inversely as the square
of the distance between the attracted particles.

Gravitation, then, is a property which is essentially inherent in
matter, and any substance which is termed matter, or fulfils the
conditions that govern matter, must be gravitative, whatever other
property it may, or may not, possess. Unless this be so, we should have
a violation of the universal Law of Gravitation, which would cease at
once to be a universal law, for instead of reading "every particle of
matter attracts every other particle," we should have to say that "some
particles of matter attract some other particles," which would be a
violation of that universal law which, through the genius