Page:Across the Zodiac (Volume 1).djvu/46

danger. But obviously, since my course lay generally in the plane of the ecliptic, and for the present at least nearly in the line joining the centres of the Earth and Sun, it was desirable that my real journey into space should commence in the plane of the midnight meridian; that is, from above the part of the Earth's surface immediately opposite the Sun. I had to reach this line, and having reached it, to remain for some time above it. To do both, I must attain it, if possible, at the same moment at which I secured a westward impulse just sufficient to counterbalance the eastward impulse derived from the rotation of the Earth;—that is, in the latitude from which I started, a thousand miles an hour. I had calculated that while directing through the main bar a current of apergy sufficient to keep the Astronaut at a fixed elevation, I could easily spare for the eastward conductor sufficient force to create in the space of one hour the impulse required, but that in the course of that hour the gradually increasing apergic force would drive me 500 miles westward. Now in six hours the Earth's rotation would carry an object close to its surface through an angle of 90°; that is, from the sunset to the midnight meridian. But the greater the elevation of the object the wider its orbit round the Earth's centre, and the longer each degree; so that moving eastward only a thousand miles an hour, I should constantly lag behind a point on the Earth's surface, and should not reach the midnight meridian till somewhat later. I had, moreover, to lose 500 miles of the eastward drift during the last hour in which I should be subject to it, through the action