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Q. D. is also frequently used, among gram marians, &c. for quasi dictum, as if it were said, &c. or as who should say.

Q, in the proper names of the Romans, signifies Quintus, or Quintius. Upon the French coins this letter denotes that they were struck at Perpignan,

QUACHA. See BARB.

centre, and are furnished either with plain sights, or a telescope, to look through. the common surveying quadrant, the astronomiThe principal and most useful quadrants, are cal quadrant, Adams's quadrant, Cole's quadrant, Collins's or Sutton's quadrant, Davis's quadrant, Gunter's quadrant, Hadley's quadrant, the horodictical quadrant, and the sinical quadrant, &c. of these in their order. See also MURAL QUA

DRANT.

1. The Common, or Surveying Quadrant.-This instrument ABC, fig. 1, pl. 147, is made of brass, or wood, &c.; the limb or arch of which BC is divided into 90°, and each of these farther divided into as many equal parts as the space will allow, either diagonally or otherwise. On one of the radii AC, are fitted two moveable sights; and to the centre is sometimes also annexed a label, or moveable index AD, bearing two other sights; but instead of these last sights, there is sometimes fitted a tele

To QUACK. v. a. (quacken, Dutch.) 1. To cry like a duck (King). 2. To chatter scope. Also from the centre hangs a thread with boastingly, to brag loudly; to talk ostentatiously (Hudibras).

QUACK. s. (from the verb.) 1. A boasted pretender to arts which he does not understand (Felton). %. A vain boasting pretender to physic; one who proclaims his own medical abilities in public places (Addison). 3. An artful tricking practitioner in physic (Pope). QUACKERY. s. (from quack.) Mean or bad acts in physic: also pretensions to any art. QUA'CKSALVER. s. (quack and salve.) One who brags of medicines or salves; a medicaster; a charlatan (Burton).

QUADI, a German nation near the country of the Marcomanni, on the borders of the Danube. They rendered themselves celebrated by their opposition to the Romans, by whom they were often defeated, though not totally subdued.

QUADRA and VANCOUVER ISLAND, an island on the N.W. coast of America, on the W. side of which is Nootka Sound. It

was so named by captain Vancouver in compliment to senor Quadra, the Spanish commandant at Nootka. It is about 300 miles in length, and 80 in its greatest breadth.

QUADRAGESIMAL. a. (quadragesimal, French; quadragesima, Latin.) Lenten; belonging to lent; used in lent (Sanderson).

QUADRANGLE. s. (quadratus and angulus, Lat.) A square; a surface with four right angles (Howel).

QUADRANGULAR. a. (from quadrangle.) Square; having four right angles (Woodward).

QUADRANT, in geometry, is either the quarter or fourth part of a circle, or the fourth part of its circumference; the arch of which, therefore, contains 90 degrees.

QUADRANT also denotes a mathematical instrument, of great use in astronomy and navigation, for taking the altitudes of the sun and stars, as also taking angles in surveying, heights and distances, &c.

This instrument is variously contrived, and furnished with different apparatus, according to the various uses it is intended for; but they have all this in common, that they consist of the quarter of a circle, whose limb or arch is divided into 90°, kc. Some have a plummet suspended from the

a plummet; and on the under side or face of the instrument is fitted a ball and socket, by means of which it may be put into any position. The general use of it is for taking angles in a vertical plane, comprehended under right lines going from the centre of the instrument, one of which is horizontal, and the other is directed to some visible point. But besides the parts above described, there is often added on the face, near the centre, a kind of compartment EF, called a quadrat, or instrument, and is particularly useful in altimetry geometrical square, which is a kind of separate

and longimetry, or heights and distances.

This quadrant may be used in different situations; in each of them the plane of the instru ment must be set parallel to that of the eye and the objects whose angular distance is to be taken. Thus, for observing heights or depths, its plane must be disposed vertically, or perpendicular to the horizon; but to take horizontal angles or distances, its plane must be disposed parallel to the

horizon.

Again, heights and distances may be taken two met, or by the label; as also, either by the degreca ways, viz. by means of the fixed sights and plum

on the limb, or by the quadrat. Thus, fig. 2, pl. 24, shews the manner of taking an angle of elevation with this quadrant; the eye is applied at C, and the instrument turned vertically about the centre A, till the object R be seen through the sights on the radius AC; then the angle of elevation RAH, made with the horizontal line KAH, is equal to the angle BAD, made by the plumb line and the other radius of the quadrant, and the

quantity of it is shewn by the degrees in the arch BD cut off by the plumb line AD.

2. The Astronomical Quadrant, is a large one, ustally made of brass or iron bars; having its limb EF (fig. 3, pl. 147) nicely divided, either diagonally or otherwise, iuto degrees, minutes, and seconds, if room will permit, and furnished either with two pair of plain sights or two telescopes, one on the side of the quadrant at AB, and the other CD moveable about the centre by means of the screw G. The dented wheels I and H serve to direct the instrument to any object or phenomenon.

The application of this useful instrument, in taking observations of the sun, planets, and fixed stars, is obvious; for being turned horizontally upon its axis, by means of the telescope AB, till the object is seen through the moveable telescope, then the degrees, &c. cut by the index, give the altitude, &c. required,

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600046949

399 d. 1839

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