ircle, or
discometer, was divided by nineteen hundred and twenty concentric
circles, equidistant from each other. The outermost, about twice as
far from the centre as from the external edge of the mirror, was
exactly equal to the Sun's circumference when presenting the largest
disc he ever shows to an observer on Earth. Each inner circle
corresponded to a diameter reduced by one second. By means of a
vernier or eye-piece, the diameter of the Sun could be read off the
discometer, and from his diameter my distance could be accurately
calculated. On the further side of the machinery was a chamber for the
decomposition of the carbonic acid, through which the air was driven
by a fan. This fan itself was worked by a horizontal wheel with two
projecting squares of antapergic metal, against each of which, as it
reached a certain point, a very small stream of repulsive force was
directed from the apergion, keeping the wheel in constant and rapid
motion. I had, of course, supplied myself with an ample store of
compressed vegetables, preserved meats, milk, tea, coffee, &c., and a
supply of water sufficient to last for double the period which the
voyage was expected to occupy; also a well-furnished tool-chest (with
wires, tubes, &c.). One of the lower windows was made just large
enough to admit my person, and after entering I had to close it and
fix it in its place firmly with cement, which, when I wished to quit
the vessel, would have again to be removed.

Of course some months were occupied in the manufacture of the
different portions of the vessel and her machinery, and sometime more
in their combination; so that when, at the end of July, I was ready to
start, the opposition was rapidly approaching. In the course of some
fifty days the Earth, moving in her orbit at a rate of about eleven
hundred miles [4] per minute, would overtake Mars; that is to say,
would pass between him and the Sun. In starting from the Earth I
should share this motion; I too should go eleven hundred miles a
minute in the same direction; but as I should travel along an orbit
constantly widening, the Earth would leave me behind. The apergy had
to make up for this, as well as to carry me some forty millions of
miles in a direction at right angles to the former--right outward
towards the orbit of Mars. Again, I should share the motion of that
particular spot of the Earth's surface from which I rose around her
axis, a motion varying with the latitude, greates