.

From the moment they had left the Earth, their own weight, and that of
the Projectile and the objects therein contained, had been undergoing a
progressive diminution. They might never be able to ascertain this fact
with regard to the Projectile, but the moment was now rapidly
approaching when the loss of weight would become perfectly sensible,
both regarding themselves and the tools and instruments surrounding
them. Of course, it is quite clear, that this decrease could not be
indicated by an ordinary scales, as the weight to balance the object
would have lost precisely as much as the object itself. But a spring
balance, for instance, in which the tension of the coil is independent
of attraction, would have readily given the exact equivalent of the
loss.

Attraction or weight, according to Newton's well known law, acting in
direct proportion to the mass of the attracting body and in inverse
proportion to the square of the distance, this consequence clearly
follows: Had the Earth been alone in space, or had the other heavenly
bodies been suddenly annihilated, the further from the Earth the
Projectile would be, the less weight it would have. However, it would
never _entirely_ lose its weight, as the terrestrial attraction would
have always made itself felt at no matter what distance. But as the
Earth is not the only celestial body possessing attraction, it is
evident that there may be a point in space where the respective
attractions may be entirely annihilated by mutual counteraction. Of this
phenomenon the present instance was a case in point. In a short time,
the Projectile and its contents would for a few moments be absolutely
and completely deprived of all weight whatsoever.

The path described by the Projectile was evidently a line from the Earth
to the Moon averaging somewhat less than 240,000 miles in length.
According as the distance between the Projectile and the Earth was
increasing, the terrestrial attraction was diminishing in the ratio of
the square of the distance, and the lunar attraction was augmenting in
the same proportion.

As before observed, the point was not now far off where, the two
attractions counteracting each other, the bullet would actually weigh
nothing at all. If the masses of the Earth and the Moon had been equal,
this should evidently be found half way between the two bodies. But by
making allowance for the difference of the respective masses, it was
easy to calculate that this po