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d into any other figure more simple than itself, as a triangle, a pyramid, etc. -- Prime meridian (Astron.), the meridian from which longitude is reckoned, as the meridian of Greenwich or Washington. -- Prime minister, the responsible head of a ministry or executive government; applied particularly to that of England…

made, generally coinciding with some principal circle of the sphere, as the equator or a meridian. -- Primitive rocks (Geol.), primary rocks. See under Primary. -- Primitive sheath. (Anat.) See Neurilemma. -- Primitive streak or trace (Anat.), an opaque and thickened band where the mesoblast first appears in the ve…

Gnomonic, etc. -- Mercator's projection, a mode of representing the sphere in which the meridians are drawn parallel to each other, and the parallels of latitude are straight lines whose distance from each other increases with their distance from the equator, so that at all places the degrees of latitude and longitud…

quadrant of one of the great circles of the globe, and graduated. It may be fitted to the meridian, and being movable round to all points of the horizon, serves as a scale in measuring altitudes, azimuths, etc.

land system of the United States, a row or line of townships lying between two succession meridian lines six miles apart.

A line which crosses successive meridians at a constant angle; -- called also rhumb line, and loxodromic curve. See Loxodromic. To sail on a rhumb, to sail continuously on one course, following a rhumb line.

To come to the meridian; to cross the north and south line; -- said chiefly of the moon; as, the moon souths at nine.

The time at which the moon, or other heavenly body, passes the meridian of a place.

The passage of a heavenly body over the meridian of a place, or through the field of a telescope.

Variation of the needle (Geog. & Naut.), the angle included between the true and magnetic meridians of a place; the deviation of the direction of a magnetic needle from the true north and south line; -- called also declination of the needle.

The distance, reckoned toward the west, between the two meridians passing through the extremities of a course, or portion of a ship's path; the departure of a course which lies to the west of north.

specially designed for determining the latitude by means of any two stars which pass the meridian about the same time, and at nearly equal distances from the zenith, but on opposite sides of it. It turns both on a vertical and a horizontal axis, is provided with a graduated vertical semicircle, and a level for setting…