something that relates to the horizon, is taken in the horizon, or on a level with the horizon.—We say, a horizontal plane, horizontal line, &c.

Horizontal Dial, is that drawn on a parallel to the horizon: having its gnomon, or style, elevated according to the altitude of the pole of the place for which it is designed. Horizontal dials are, of all others, the most simple and easy. The manner of describing them, see under the article Dial.