But the moon is not always at her zenith when she reaches her perigee, which is once a month.

She is only under the two conditions simultaneously at long intervals of time.

This coincidence of perigee and zenith must be waited for.

It happens fortunately that on December 4th of next year the moon will offer these two conditions; at midnight she will be at her perigee and her zenith--that is to say, at her shortest distance from the earth and at her zenith at the same time.
"Regarding question No.

5, 'At what point in the heavens ought the cannon destined to hurl the projectile be aimed ?' "The preceding observations being admitted, the cannon ought to be aimed at the zenith of the place (the zenith is the spot situated vertically above the head of a spectator), so that its range will be perpendicular to the plane of the horizon, and the projectile will pass the soonest beyond the range of terrestrial gravitation.