an arch, or part of the meridian of the place, terminated each way by the horizon. Or, a meridian line is the intersection of the plane of the meridian of the place with the plane of the horizon, often called a north-and-south line, because its direction is from north to south.

In the article Astronomy (Encycl.), no. 376 and 377, we have given two methods of drawing a meridian line; but it may be proper to add, in this place, the following improvement of the former of these from Dr Hutton's Mathematical Dictionary. "As it is not easy (says the Doctor) to determine precisely the extremity of the shadow, it will be best to make the file flat at the top, and to drill a small hole through it, noting the lucid point projected by it on the several concentric circles, instead of marking the extremity of the shadow itself on these circles."

We shall give another method of drawing a meridian line from the same valuable dictionary.

"Knowing the fourth quarter pretty nearly, observe the altitude FE of some star on the east side of it, and not far from the meridian HZRN: then, keeping the quadrant firm on its axis, so as the plummet may fall cut the same degree, direct it to the western side of the meridian, and wait till you find the star has the same altitude as before, as fe. Lastly, bisect the angle EC, formed by the intersection of the two planes in which the quadrant has been placed at the time of the two observations, by the right line HR, which will be the meridian sought."

Magnetical Meridian, is a great circle passing thro' or by the magnetical poles; to which meridians the magnetical needle conforms itself. See Magnetism, Suppl.