Page:Across the Zodiac (Volume 1).djvu/68

 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 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.