subdivided into half points and quarter points, as shown in Fig. 10. The four principal points are named after the principal horizon points-north, east, south, and west-and are usually termed the cardinal points; while the points midway between the cardinals are called the intercardinals or quadrantal points. Each point has a name, and these the student should learn so as to be able to repeat them in regular order from north around by way of east and back to north, and vice versa. This procedure, commonly known. as "boxing the compass," will, with the aid of Fig. 10, be comparatively easy.

39. Commencing from the north point at the top of the card and going round to the right, or in the direction in which the hands of a watch move, the names of the points are as follows: North, north-by-east, north-northeast, northeastby-north, northeast, northeast-by-east, east-northeast, east-bynorth; East, east-by-south, east-southeast, southeast-by-east, southeast, southeast-by-south, south-southeast, south-by-east; South, south-by-west, south-southwest, southwest-by-south, southwest, southwest-by-west, west-southwest, west-by-south; West, west-bynorth, west-northwest, northwest-by-west, northwest, northwestby-north, north-northwest, north-by-west, north.

From this it can be seen that the cardinal points are eight points away from each other, and four points away from the nearest quadrantal point. The name of the opposite point. to any given point is known at once by simply reversing the name or the letters that indicate the name of the given point. Thus, the opposite point of NE by E is SW by W, that of N NW is SS E, that of E by S is W by N, and so on.

40. The space between each point is divided into four equal parts called half and quarter points. Thus, an expression NW means north a quarter point to the west, and SE by EE means southeast-by-east three-quarter point to the east. There is no particular system in expressing half and quarter points, but experience has taught that the simplest is the best. Hence, the expression N N EE

TABLE II

TABLE SHOWING THE NAMES OF POINTS AND THE NUMBER OF DEGREES, MINUTES, AND SECONDS CORRESPONDING TO ANY NUMBER OF POINTS AND FRACTION THEREOF

is preferable to NE by NN, though both indicate the same point; and, likewise, N by EE is preferable to N N E N. Absurdities like W by NW and N by E N should never be used.

41. Quite frequently a ship's course is given in degrees, especially on steamships, as they can be steered more closely than a sailing vessel, and a course of this kind is expressed as so many degrees east or west from either north or south, as N 23° E, S 48° W, S 60° E, etc. The table on page 19, showing relation between points and degrees, will be very convenient to refer to when it is desired to convert courses expressed in degrees into points, and vice versa.

42. The compass bowl is generally made of brass or copper, the last named metal being preferable on account of its tendency to dampen or diminish the oscillations of the

card. On the inside of the bowl is a vertical line called the lubber line or lubber's point (see a Fig. 11), which, with the center of the bowl, or the card, indicates the direction of the ship's longitudinal center line. The pivot, which is of a conical form, should be screwed into the exact center of the bowl, and its point should be made of some hard metal, preferably of bell metal. The bowl, which is sufficiently large to admit of the card moving freely, is weighted at the bottom and fitted with gimbals, so that the card may always preserve a horizontal position even when the motion of the ship is most violent.

FIG. 11

43. The binnacle, Fig. 12, is a stand firmly secured to the deck in front of the helmsman's position (in case the compass it contains is used for steering), or in any other

suitable position where disturbing forces will have the least effect on the compass. It is made either of wood or brass and may be of any shape-round, square, or octagonal. Within it are supports on which are placed the gimbals of the compass bowl. The top of the binnacle, which is movable, is furnished with

glass so that the card may be seen, and also with lamps at the sides to light up the card at night.

44. Sir William Thompson's Compass. Among the many good compasses in use today may be mentioned Sir William Thompson's, patented in 1876. Its principal features are as follows: A thin aluminum ring (see Fig. 10) is connected by radial silk threads to an aluminum cap having a center piece. of sapphire poised on an iridium point. Instead of one single needle, there are not less than eight strips of magnetized steel fastened to the silk threads, as shown in the figure. The paper rim bearing the points is divided at intervals so that the contractions and expansions due to change of temperature may not produce warping of the aluminum. The entire weight of the whole arrangement is about 170 grains, which is little more than of an ounce, and but the weight of the ordinary 10-inch compass previously in common use on merchant steamers and large sailing ships. The bowl of this compass is saved from

FIG. 12

violent oscillations by having in its bottom a quantity of castor oil, while a simple device prevents the card from jumping off the pivot when heavy guns are fired. The binnacle has complete provisions for stowing away the magnets, soft iron bars, and spheres used to counteract the magnetism of the iron surrounding the compass.

45. The requirements of a perfect compass may be summed up as follows:

1. The pivot and the cap working upon it should be accurately in the center of the bowl as well as in the center of the card.

2. The divisions of the card, particularly the points, should be perfect.

3.

The direction of the magnetism of the needle or needles should be parallel to the north and south line of the card.

4. The compass should be comparatively steady when subjected to the rolling and pitching motions of the ship and sensitive when at rest or when the ship is in smooth water.

46. Care of Compasses.-In order that the compass may be as faultless as possible, the pivot, cap, and margins of the card should be frequently examined to see that they are in good order and working freely; and when the card works sluggishly or an injury from any cause occurs, a new cap or pivot should be put in, taking good care when screwing the pivot into the bowl to preserve its point from injury and to place the card lightly upon it. When the bowl does not work freely in the gimbals, the axis of the latter and their bushings should be examined, and, if necessary, slightly rubbed with plumbago or graphite. No oil, grease, or other fatty substances should be used for this purpose.

47. According to the use to which the mariner's compass is applied on board ship it is called the steering compass, the standard compass, or the azimuth compass.

48. The steering compass is the one used by the helmsman, and by which the ship is steered in a certain direction. The requirements of this compass, as well as of