VERNIER, or Nonius. A graduated scale for the measurement of minute divisions, especially on the arcs of astronomical instruments, sextants, &c. The thousandth part of a degree can be taken by the naked eye; the ten thousandth by a microscope.
VERSED SINE. In geometry, is the part of the radius intercepted between the arc and its sine.
VERTEX. The zenith, the point overhead; the apex of a conical mountain.
VERTICAL ANGLES. Opposite angles made by two lines cutting or crossing each other, and are always equal. (See [Angle of the Vertical].)
VERTICAL CIRCLES. Great circles of the sphere intercepting each other in the zenith and nadir, and cutting the horizon at right angles.
VERTICAL FIRE. In artillery, that directed upward at such an angle as that it will fall vertically, or nearly so, to its destination. It includes all elevations above 30°, though the most usual is 45°. It is very effective with shells; but with small balls, as proposed by Carnot and others, who have ill reckoned the retardation by the atmosphere, it is insignificant.
VERTICAL FORCE. The centre of displacement is also that of the centre of vertical force that the water exerts to support the immersed vessel. Also, the dip of the magnetic needle, measured by vibrations of the dipping needle over certain arcs, and referable to some fixed position, as Greenwich, where corresponding observations with the same needle have been previously, as well as subsequently, made.
VERTICAL PLAN. See [Orthographic Projection].
VERTICITY. The tendency of the loadstone to point towards the magnetic north and south.
VESSEL. A general name for all the different sorts of ships, boats, &c., navigated on the ocean or on rivers and canals.