MURAL ARCH, a wall, or walled arch, placed exactly in the plane of the meridian line for fixing a large quadrant, sextant, or other instrument, to observe the meridian altitudes, etc., of the heavenly bodies.
Edition of 1921; disclaimer.
MURAL ARCH, a wall, or walled arch, placed exactly in the plane of the meridian line for fixing a large quadrant, sextant, or other instrument, to observe the meridian altitudes, etc., of the heavenly bodies.