Note:  Do not rely on this information. It is very old.


Horizon, Artificial, is a basin of mercury protected so that its surface shall remain clean and unruffled. Celestial objects reflected from the surface of the mercury appear to the eye as though they were at as great a distance below the horizon as they are actually above it. On account of-this fact, a knowledge of the actual position of the horizon may be dispensed with - a matter of much convenience on land.