Arctic Manual, page 739.]

As to gravity, no one knows what it is, because it has not been
determined whether it is atmospheric pressure that causes the
apple to fall, or whether, 150 miles below the surface of the
earth, supposedly one-half way through the earth's crust, there
exists some powerful loadstone attraction that draws it.
Therefore, whether the apple, when it leaves the limb of the
tree, is drawn or impelled downward to the nearest point of
resistance, is unknown to the students of physics.

Sir James Ross claimed to have discovered the magnetic pole at
about seventy-four degrees latitude. This is wrong -- the
magnetic pole is exactly one-half the distance through the
earth's crust. Thus, if the earth's crust is three hundred miles
in thickness, which is the distance I estimate it to be, then the
magnetic pole is undoubtedly one hundred and fifty miles below
the surface of the earth, it matters not where the test is made.
And at this particular point one hundred and fifty miles below
the surface, gravity ceases, becomes neutralized; and when we
pass beyond that point on toward the "inside" surface of the
earth, a reverse attraction geometrically increases in power,
until the other one hundred and fifty miles of distance is
traversed, which would bring us out on the "inside" of the earth.

Thus, if a hole were bored down through the earth's crust at
London, Paris, New York, Chicago, or Los Angeles, a distance of
three hundred miles, it would connect the two surfaces. While the
inertia and momentum of a weight dropped in from the "outside"
surface would carry it far past the magnetic center, yet, before