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

Pupil. I have, Sir.

Tutor. Of what figure was the darkened part?

Pupil. Circular.

Tutor. Take this ball, and hold it before the candle between your finger and thumb, so that the shadow may be thrown on the wall, and in all positions you will find it circular.

Pupil. It is so.

Tutor. Apply this crown piece in the same manner, with the flat side to the candle.

Pupil. It is a circle.

Tutor. Turn it a little obliquely.

Pupil. It is now an ellipsis.

Tutor. Now turn the edge to the candle.