David Rittenhouse quotes:

But Dr. Smith says, and I believe it to be a true state of the case, that he himself gave a course of Lectures in Natural Philosophy, during the same winter, and that the money raised by them was also applied towards paying for the Orrery.

For the greater beauty of the instrument, the balls representing the planets are to be of considerable bigness; but so contrived, that they may be taken off at pleasure, and others, much smaller, and fitter for some purposes, put in their places.

In order to know the true situation of a Planet at any particular time, the small set of balls are to be put each on its respective axis; then the winch to be turned round until each index points to the given time.