"Out of Bristowe and costes many one,
Men haue practised by nedle and by stone
Thider wardes within alitle while."
Hakluyt, Principal Navigations, p. 201, Lond. 1599.
From this it would seem that the compasses used at that time by English mariners were of a very primitive description. Barlowe, in his treatise Magnetical Advertisements, printed in 1616 (p. 66), complains that "the Compasse needle, being the most admirable and usefull instrument of the whole world, is both amongst ours and other nations for the most part, so bungerly and absurdly contrived, as nothing more." The form he recommends for the needle is that of "a true circle, having his Axis going out beyond the circle, at each end narrow and narrower, unto a reasonable sharpe point, and being pure steele as the circle it selfe is, having in the middest a convenient receptacle to place the capitell in." In 1750 Dr Gowan Knight found that the needles of merchant-ships were made of two pieces of steel bent in the middle and united in the shape of a rhombus, and proposed to substitute straight steel bars of small breadth, suspended edgewise, and hardened throughout. He also showed that the Chinese mode of suspending the needle conduces most to sensibility. In 1820 Prof. Barlow reported to the Admiralty that half the compasses in the Royal Navy were mere lumber, and ought to be destroyed. Since then many improved varieties of ships compasses have been introduced, of which may be mentioned those of Pope, Preston, Walker, Dent, Stebbing, Gowland, Gray, Duchemin, and Harris. In the last the needle turns upon a point which is the centre of a doubly-curved bar of copper, fixed as a diameter to a ring of the same metal. In the Admiralty compass the bowl is of copper, the card of mica; and compound magnetic bars, as proposed by Scoresby, are employed.}}
Fig. 2.—Plan and Transverse Section of Sir William Thomson's Compass-card.
B, Corrector for quadrantal error; C, Box for corrector; a, Aluminium boss; b. Central cap of sapphire; c, Cords connecting rim and boss; d, Magnets e, Threads connecting magnets; f, Aluminium rim; f′, Cords supporting magnets; g.g′. Knife edges for gimbals.
The most remarkable and, as shown by trial, most satisfactory form of the compass is that patented in 1876 by Sir William Thomson (see fig. 2). The card consists of a central boss and an outer rim, both of aluminium, connected together by fine silk cords. Eight or twelve small magnets, 2 to 3 inches long, having their corresponding ends tied together by threads of equal lengths, are suspended by silk cords from the rim, to which is attached thin paper marked with the points of the compass and degrees. The concentration, in this wise, of the greater part of the weight in the rim gives a long period of free oscillation, and consequently great steadiness; and as the card of a 10-inch compass, with its suspended needle and sapphire, weighs only 178 grains, the frictional error is very slight. Owing to the smallness of the needles, a perfect correction for all latitudes of a quadrantal error of 5 or 6 degrees for a 10-inch, and of 11 or 12 degrees for a 7-inch compass can be effected by means of a couple of iron globes not more than 6 inches in diameter, fixed on opposite sides of the binnacle. The thwart-ship and the fore-and-aft components of the ship's magnetic force are neutralized by two adjustable correctors placed one over the other, and so arranged that in their zero position the middle line of both is vertically under the centre of the compass. Each corrector consists of two bar magnets movable round a common horizontal axis perpendicular to their lengths. To correct the heeling error, an adjustable magnet is applied below the compass in a line through its centre perpendicular to the deck. For taking bearings, a new instrument, the azimuth mirror, is provided, whereby the image of the object reflected from a plane mirror is thrown, as in a camera lucida, on the graduated circle of the compass card, and is seen through a convex lens. Another improvement is the use of knife edges instead of journals for supporting the gimbals. A hemispherical space below the compass-case, nearly filled with castor-oil, serves to calm the vibrations of the bowl.
See articles Magnetism and Navigation; Cavallo, Treatise on Magnetism, 2d ed., Lond. 1800; Macpherson, Annals of Commerce, 1805; Airy, Phil. Trans., 1839, and 1846, part i., and Magnetism, sect, x., 1870; Johnson, On the Deviations of the Compass, 1852; Evans, Phil. Trans., 1860; Scoresby, The Compass in Iron Ships, 1855, &c.; Evans and Smith, The Admiralty Manual of the Compass; Merrifield, Magnetism and the Deviation of the Compass, part ii., 1872; Harris, Rud. Treat. on Magnetism, 1872; Thomson, in Nature, vol. x. p. 388, 1874.
COMPIÈGNE, a town of France, at the head of an arrondissement, in the department of Oise, situated on the left bank of the Oise, which is there crossed by a handsome bridge of three arches, 36 miles east of Beauvais, on the railway between Paris and St Quentin, in 49º 25′ 4′′ N. lat. and 2º 49′ 35′′ E. long. It is famous as the occasional residence of the French kings from a very early period; and it possesses a considerable number of fine edifices. Among these may be mentioned the church of St Jacques, of the 13th century; Saint Antoine, of the 15th and 16th; the town-house, a picturesque building of the late Gothic style, dating from the 16th; the theatre; and the royal palace, which is one of the most extensive and magnificent structures of the kind in France. It wag erected mainly under Louis XV. and XVI., but large additions have been made in more recent times. The gardens are beautifully laid out, and in the neighbourhood is the famous forest of Compiègne, which covers an area of 30,000 acres, and includes the site of the camp constructed by Cæsar in his campaign against the Bellovaci. The town is the seat of a civil and a commercial tribunal, and has a communal college, a public library, and a museum in the town-hall. The principal manufactures are hosiery, muslins, ropes, and wooden wares; and there is a fair trade in corn and wood. Population in 1872, 11,859 in the town, and 12,281 in the commune.
Compiègne, or, as it is called in the Latin chronicles, Compendium, seems originally to have been a hunting-lodge of the early Frankish kings. It was enriched by Charles the Bald with two castles, and a Benedictine abbey dedicated to Saint Corneille, the monks of which retained down to the 18th century the privilege of acting for three days as lords of Compiègne, with full power to release prisoners, condemn the guilty, and even inflict sentence of death. It was in Compiègne that Louis the Debonnaire was deposed in 833; and at the siege of the town in 1430, Joan of Arc was taken prisoner by the English. The abbey church received the dust of Louis II., Louis V., and Hugh the Great; and for a long time it had the distinction of possessing the oldest organ in France, a gift from Constantine Copronymus to Pepin the Short. In 1624 the town gave its name to a treaty of alliance concluded by Richelieu with the Dutch; and it was in the palace that Louis XV. gave welcome to Marie Antoinette, that Napoleon I. received Marie Louise of Austria, that Louis XVIII. entertained the Emperor Alexander of Russia, and that Leopold king of the Belgians was married to the Princess Louise. Under Napoleon III. it was the annual resort of the court during the hunting season, and thus became the scene of many a remarkable assembly. In 1871 the town was an important post of communication between France and Germany.
