Plate viii to face QUARTER
Q.
QUADRANT, an instrument used to take the altitude of the sun or stars at sea, in order to determine the latitude of the place; or the sun’s azimuth, so as to ascertain the magnetical variation.
These instruments are variously constructed, and by consequence the apparatus of each kind is somewhat different from those of the others, according to the improvements they have at different times received from several ingenious artists.
As all the different kinds of quadrants are circumstantially described, either in printed directions to use them, or in other books, a particular account of them here might reasonably be esteemed superfluous. It suffices to say that the most useful, as well as the most general, for taking observations at sea is the octant, originally invented by Sir Isaac Newton, and since that time improved and brought into practice by Mess. Godfrey and Hadley. It may not however be unnecessary to remark, that the back-observation, which, in many situations, is certainly more accurate and useful than that which is taken in front, is almost totally neglected by our observers, under pretence of its being more uncertain, or more liable to error: but really because it is somewhat more difficult to learn. We may venture to affirm however, that no artist, who thoroughly understands the operation, will ever advance so absurd an objection, unless we should doubt the testimony of a multitude of experiments.
QUARANTINE, the state of the persons who are restrained within the limits of a ship, or lazaretto; or otherwise prevented from having a free communication with the inhabitants of any country, till the expiration of an appointed time, during which they are repeatedly examined with regard to their health. It is chiefly intended to prevent the importation of the plague, from the countries under the dominion of the Turks.
QUARTER of a ship, hanche, that part of a ship’s side which lies towards the stern, or which is comprehended between the aftmost end of the main chains and the sides of the stern, where it is terminated by the quarter-pieces.
Although the lines by which the quarter and bow of a ship, with respect to her length, are only imaginary, yet experience appears sufficiently to have ascertained their limits: so that if we were to divide the ship’s sides into five equal portions, the names of each space would be readily enough expressed. Thus the first, from the stern, would be the quarter; the second, abaft the midships; the third, the midships; the fourth, before the midships; and the fifth, the bow. Whether these divisions, which in reality are somewhat arbitrary, are altogether improper, may be readily discovered by referring to the mutual situation or approach of two adjacent vessels. The enemy boarded us on the larboard-side! Whereabouts? Abaft the midships, before the midships, &c.
Plate [VIII]. fig. 3. represents a geometrical elevation of the quarter of a 74 gun ship, as corresponding with the other figures of a ship of the same rate, delineated upon the same plate. See the articles Head, Midship-Frame, and Stern.