from The Century Dictionary and Cyclopedia
- n. In astronomy: Any great circle of the sphere which passes through the two poles: so called because the hour of the day is ascertained when the circle upon which the sun is for the time being is ascertained.
- n. A circle upon an equatorial telescope lying parallel to the plane of the earth's equator, and graduated into hours and subdivisions of hours.
Sorry, no etymologies found.
In both these collections the distances separating the individuals of each pair were carefully measured, and (with a few exceptions) the angles made with the hour-circle by the lines joining their centres (technically called