nd then
what looked like a silver terrestrial crescent, but a mere thread,
finer and shorter than any that the Moon ever displays even to
telescopic observers on Earth; since, when such a minute portion of
her illuminated surface is turned towards the Earth, it is utterly
extinguished to our eyes by the immediate vicinity of the Sun, as was
soon the case with the terrestrial crescent in question. I watched
long and with intense interest the gradual change, but I was called
away from it by a consideration of no little practical moment. I must
now be moving at a rate of nearly, if not quite, 40,000 miles an hour,
or about a million miles per diem. It was not my intention, for
reasons I shall presently explain, ever greatly to exceed this rate;
and if I meant to limit myself to a fixed rate of speed, it was time
to diminish the force of the apergic current, as otherwise before its
reduction could take effect I should have attained an impulse greater
than I desired, and which could not be conveniently or easily
diminished when once reached. Quitting, therefore, though reluctantly,
my observation of the phenomena below me, I turned to the apergion,
and was occupied for some two or three hours in gradually reducing the
force as measured by the cratometer attached to the downward
conductor, and measuring with extreme care the very minute effect
produced upon the barycrite and the discometer. Even the difference
between 200 and 201 radii of elevation or apogaic distance was not
easily perceptible on either. It took, of course, much more minute
observation and a much longer time to test the effect produced by the
regulation of the movement, since whether I traveller forty,
forty-five, or forty-two thousand miles in the course of one hour made
scarcely any difference in the diameter of the Earth's disc, still
less, for reasons above given, in the gravity. By midnight, however, I
was satisfied that I had not attained quite 1,000,000 miles, or 275
terrestrial radii; also that my speed was not greater than 45,000
miles (11-1\4 radii) per hour, and was not, I thought, increasing. Of
this last point, however, I could better satisfy myself at the end of
my four hours' rest, to which I now betook myself.

I woke about 4h. 30m., and on a scrutiny of the instruments, felt
satisfied that I was not far out in my calculations. A later hour,
however, would afford a more absolute certainty. I was about to turn
again to the interesting work of