Prolonged observation and careful calculation had so fully satisfied me of the necessity of the corrections in question, that I did not hesitate to alter my course accordingly, and to prepare for a descent on the thirty-ninth instead of the forty-first day.

I had, of course, to prepare for the descent very long before I should come within the direct influence of the attraction of Mars.

This would not prevail over the Sun's attraction till I had come within a little more than 100,000 miles of the surface, and this distance would not allow for material reduction of my speed, even were I at once to direct the whole force of the apergic current against the planet.

I estimated that arriving within some two millions of miles of him, with a speed of 45,000 miles per hour, and then directing the whole force of the current in his direction, I should arrive at his surface at a speed nearly equal to that at which I had ascended from the Earth.

I knew that I could spare force enough to make up for any miscalculation possible, or at least probable.