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 observation through the lens in the floor, when my attention was diverted by the sight of something like a whitish cloud visible through the upper window on my left hand.  Examined by the telescope, its widest diameter might be at most ten degrees.  It was faintly luminous, presenting an appearance very closely resembling that of a star cluster or nebula just beyond the power of resolution.  As in many nebulae, there was a visible concentration in one part; but this did not occupy the centre, but a position more resembling that of the nucleus of a small tailless comet.  The cloudlet might be a distant comet, it might be a less distant body of meteors clustering densely in some particular part of their orbit; and, unfortunately, I was not likely to solve the problem.  Gradually the nebula changed its position, but not its form, seeming to move downwards and towards the stern of my vessel, as if I were passing it without