The Study of Astronomy, adapted to the capacities of youth / In twelve familiar dialogues, between a tutor and his pupil: explaining the general phænomena of the heavenly bodies, the theory of the tides, &c.

by teacher of astronomy John Stedman

DIALOGUE VII.

Tutor.

Having at our last meeting explained to you the nature of the attractive and projectile forces, I shall proceed to shew you that it is by the joint action or combination of these two forces that the planets are retained in their orbits.

Pupil. I am all anxiety, as I wish to be informed how, or in what manner they can act against each other, to produce that effect.

Tutor. Answer me a few questions, and you will soon know.

Pupil. As many as you please, Sir.

Tutor. If you whirl a stone in a sling, what will be its motion?

Pupil. Circular.

Tutor. Is you let it suddenly slip out of the sling, will it continue its circular motion?

Pupil. No, Sir, but fly off in a strait line.