"This perseverance of a body in a state of rest can only take place in
absolute space, and can then only be intelligible by admitting it." In
dealing with the physical cause of Gravitation, I hope to be able to
show that it can not only be admitted as a mathematical proposition, but
that it can be made intelligible from the physical standpoint.

The second part of the First Law of Motion may be stated as follows:
"Every body continues in a state of uniform motion in a straight line,
except in so far as it is compelled by impressed forces to change that
state."

Now what is the testimony of observation and experiment in regard to
this part of the First Law of Motion? Let us test the question by the
results of our experience. If a ball is sent rolling along the ground,
its motion is gradually reduced until it comes to rest. If the ground is
very rough indeed, as for example a ploughed field, then its speed will
be very soon reduced, and the ball quickly comes to a standstill. If,
however, the ground is smooth and level, like a well-kept cricket-field,
then the motion of the ball will be reduced more slowly, and it will
travel further before being brought to rest; while, if the ball is
thrown along a very smooth surface of ice, it will travel a much longer
distance before it is finally brought to rest.

Thus we learn, that the more we can get rid of all resistances to the
motion of any body, the greater distance will the body travel, and the
less diminution there is in the uniform motion of the body. So that, if
it were possible to obtain a medium which offered no resistance at all
to a moving body, then it would be a legitimate inference to infer that
a body in such a medium, when once set in motion, would move with
uniform motion for ever. Under such conditions, therefore, this part of
Newton's First Law of Motion is physically conceivable. The crux of the
whole matter, therefore, lies in the problem as to whether there is, or
there is not, in existence, such a thing as a frictionless medium. We
will therefore consider the problem of the existence of a frictionless
medium from the philosophical standpoint.

Professor Lodge, in _Modern Views of Electricity_, p. 331, writes: "Now,
if there is one thing with which the human race has been more conversant
than another, and concerning which more experience has been
unconsciously accumulated than about almost anything else that can be
mentioned, it is the action of one body