DORMER

, or Dormant, in Architecture, denotes a window made in the roof of a building, or above the entablature; being raised upon the rafters.

DOUBLE Aspect, Bastion, Concave, Convex, Cone, Descant, Eccentricity, Position, Ratio, Tenaille, &c. See the respective words.

Double Horizontal Dial, one with a double gnomon, the one pointing out the hour on the outer circle, the other the hour on the stereographic projection drawn upon it. This dial finds the meridian, the hour, the sun's place, rising, setting, &c, and many other problems of the globe.

Double Point, in the Higher Geometry, is a point which is common to two parts or legs or branches of some curve of the 2d or higher order: such as, an infinitely small oval, or a cusp, or the cruciform intersection, &c, of such curves. See Newton's Enumeratio Linearum &c, de Curvarum Punctis Duplicibus.

Doubling a Cape, or Point of Land, in Navigation, signifies the coming up with it, passing by it, and leaving it behind the ship.

The Portuguese pretend that they first doubled the Cape of Good Hope, under their admiral Vasquez de Gama; but there are accounts in history, particularly in Herodotus, that the Egyptians, Carthaginians, &c, had done the same long before them.