Fig. 5.—Liquid Compass.A, Bowl, partly in section.N, Hole for filling, with screw plug.B, Expansion chamber.O, O, Magnetic needles.D, The glass.P, Buoyant chamber.G, Gimbal ring.Q, Iridium pivot.L, Nut to expand chamber when filling bowl.R, Sapphire cap.M, Screw connector.S, Mica card.
Great steadiness of card under severe shocks and vibrations, combined with a minimum of friction in the cap and pivot, is obtained with this compass. All compasses are fitted with a gimbal ring to keep the bowl and card level under every circumstance of a ship’s motion in a seaway, the ring being connected with the binnacle or pedestal by means of journals or knife edges. On the inside of every compass bowl a vertical black line is drawn, called the “lubber’s point,” and it is imperative that when the compass is placed in the binnacle the line joining the pivot and the lubber’s point be parallel to the keel of the vessel. Thus, when a degree on the card is observed opposite the lubber’s point, the angle between the direction in which the ship is steering and the north point of the compass or course is at once seen; and if the magnetic variation and the disturbing effects of the ship’s iron are known, the desired angle between theship’scourse and the geographical meridian can be computed. In every ship a position is selected for the navigating or standard compass as free from neighbouring iron as possible, and by this compass all courses are shaped and bearings taken. It is also provided with an azimuth circle or mirror and a shadow pin or style placed in the centre of the glass cover, by either of which the variable angle between the compass north and true north, called the “total error,” or variation and deviation combined, can be observed. The binnacles or pedestals for compasses are generally constructed of wood about 45 in. high, and fitted to receive and alter at pleasure the several magnet and soft iron correctors. They are also fitted with different forms of suspension in which the compass is mounted to obviate the mechanical disturbance of the card caused by the vibration of the hull in ships driven by powerful engines.
The effects of the iron and steel used in the construction of ships upon the compass occupied the attention of the ablest physicists of the 19th century, with results which enable navigators to conduct their ships with perfect safety. The hull of an iron or steel ship is a magnet, and the distribution of its magnetism depends upon the direction of the ship’s head when building, this result being produced by induction from the earth’s magnetism, developed and impressed by the hammering of the plates and frames during the process of building. The disturbance of the compass by the magnetism of the hull is generally modified, sometimes favourably, more often unfavourably, by the magnetized fittings of the ship, such as masts, conning towers, deck houses, engines and boilers. Thus in every ship the compass needle is more or less subject to deviation differing in amount and direction for every azimuth of the ship’s head. This was first demonstrated by Commander Matthew Flinders by experiments made in H.M.S. “Investigator” in 1800-1803, and in 1810 led that officer to introduce the practice of placing the ship’s head on each point of the compass, and noting the amount of deviation whether to the east or west of the magnetic north, a process which is in full exercise at the present day, and is called “swinging ship.” When speaking of the magnetic properties of iron it is usual to adopt the terms “soft” and “hard.” Soft iron is iron which becomes instantly magnetized by induction when exposed to any magnetic force, but has no power of retaining its magnetism. Hard iron is less susceptible of being magnetized, but when once magnetized it retains its magnetism permanently. The term “iron” used in these pages includes the “steel” now commonly employed in shipbuilding. If an iron ship be swung when upright for deviation, and the mean horizontal and vertical magnetic forces at the compass positions be also observed in different parts of the world, mathematical analysis shows that the deviations are caused partly by the permanent magnetism of hard iron, partly by the transient induced magnetism of soft iron both horizontal and vertical, and in a lesser degree by iron which is neither magnetically hard nor soft, but which becomes magnetized in the same manner as hard iron, though it gradually loses its magnetism on change of conditions, as, for example, in the case of a ship, repaired and hammered in dock, steaming in an opposite direction at sea. This latter cause of deviation is called sub-permanent magnetism. The horizontal directive force on the needle on board is nearly always less than on land, sometimes much less, whilst in armour-plated ships it ranges from .8 to .2 when the directive force on land = 1.0. If the ship be inclined to starboard or to port additional deviation will be observed, reaching a maximum on north and south points, decreasing to zero on the east and west points. Each ship has its own magnetic character, but there are certain conditions which are common to vessels of the same type.
Instead of observing the deviation solely for the purposes of correcting the indications of the compass when disturbed by the iron of the ship, the practice is to subject all deviations to mathematical analysis with a view to their mechanical correction. The whole of the deviations when the ship is upright may be expressed nearly by five co-efficients, A, B, C, D, E. Of these A is a deviation constant in amount for every direction of the ship’s head. B has reference to horizontal forces acting in a longitudinal direction in the ship, and caused partly by the permanent magnetism of hard iron, partly by vertical induction in vertical soft iron either before or abaft the compass. C has reference to forces acting in a transverse direction, and caused by hard iron. D is due to transient induction in horizontal soft iron, the direction of which passes continuously under or over the compass. E is due to transient induction in horizontal soft iron unsymmetrically placed with regard to the compass. When data of this character have been obtained the compass deviations may be mechanically corrected to within 1°—always adhering to the principal that “like cures like.” Thus the part of B caused by the permanent magnetism of hard iron must be corrected by permanent magnets horizontally placed in a fore and aft direction; the other part caused by vertical soft iron by means of bars of vertical soft iron, called Flinders bars, before or abaft the compass. C is compensated by permanent magnets athwart-ships and horizontal; D by masses of soft iron on both sides of the compass, and generally in the form of cast-iron spheres, with their centres in the same horizontal plane as the needles; E is usually too small to require correction; A is fortunately rarely of any value, as it cannot be corrected. The deviation observed when the ship inclines to either side is due—(1) to hard iron acting vertically upwards or downwards; (2) to vertical soft iron immediately below the compass; (3) to vertical induction in horizontal soft iron when inclined. To compensate (1)vertical magnets are used; (3) is partly corrected by the soft iron correctors of D; (2) and the remaining part of (3) cannot be conveniently corrected for more than one geographical position at a time. Although a compass may thus be made practically correct for a given time and place, the magnetism of the ship is liable to changes on changing her geographical position, and especially so when steaming at right angles or nearly so to the magnetic meridian, for then sub-permanent magnetism is developed in the hull. Some vessels are more liable to become sub-permanently magnetized than others, and as no corrector has been found for this source of deviation the navigator must determine its amount by observation. Hence, however carefully a compass may be placed and subsequently compensated, the mariner has no safety without constantly observing the bearings of the sun, stars or distant terrestrial objects, to ascertain its deviation. The results of these observations are entered in a compass journal for future reference when fog or darkness prevails.
Every compass and corrector supplied to the ships of the British navy is previously examined in detail at the Compass Observatory established by the admiralty at Deptford. A trained observer acting under the superintendent of compasses is charged with this important work. The superintendent, who is a naval officer, has to investigate the magnetic character of the ships, to point out the most suitable positions for the compasses when a ship is designed, and subsequently to keep himself informed of their behaviour from the time of the ship’s first trial. A museum containing compasses of various types invented during the 19th century is attached to the Compass Observatory at Deptford.
The mariner’s compass during the early part of the 19th century was still a very imperfect instrument, although numerous inventors had tried to improve it. In 1837 the Admiralty Compass Committee was appointed to make a scientific investigation of the subject, and propose a form of compass suitable alike for azimuth and steering purposes. The committee reported in July 1840, and after minor improvements by the makers the admiralty compass, the card of which is shown in figs. 1 and 2, was adopted by the government. Until 1876, when Sir William Thomson introduced his patent compass, this compass was not only the regulation compass of the British navy, but was largely used in other countries in the same or a modified form. The introduction of powerful engines causing serious vibration to compass cards of the admiralty type, coupled with the prevailing desire for larger cards, the deviation of which could also be more conveniently compensated, led to the gradual introduction of the Thomson compass. Several important points were gained in the latter: the quadrantal deviation could be finally corrected for all latitudes; frictional error at the cap and pivot was reduced to a minimum, the average weight of the card being 200 grains; the long free vibrational period of the card was found to be favourable to its steadiness when the vessel was rolling. The first liquid compass used in England was invented by Francis Crow, of Faversham, in 1813. It is said that the idea of a liquid compass was suggested to Crow by the experience of the captain of a coasting vessel whose compass card was oscillating wildly until a sea broke on board filling the compass bowl, when the card became steady. Subsequent improvements were made by E. J. Dent, and especially by E. S. Ritchie, of Boston, Massachusetts. In 1888 the form of liquid compass (fig. 5) now solely used in torpedo boats and torpedo boat destroyers was introduced. It has also proved to be the most trustworthy compass under the shock of heavy gun fire at present available. The deflector is an instrument designed to enable an observer to reduce the deviations of the compass to an amount not exceeding 2° during fogs, or at any time when bearings of distant objects are not available. It is certain that if the directive forces on the north, east, south and west points of a compass are equal, there can be no deviation. With the deflector any inequality in the directive force can be detected, and hence the power of equalizing the forces by the usual soft iron and magnet correctors. Several kinds of deflector have been invented, that of Lord Kelvin (Sir William Thomson) being the simplest, but Dr Waghorn’s is also very effective. The use of the deflector is generally confined to experts.The Magnetism of Ships.—In 1814 Flinders first showed (see Flinders’sVoyage, vol. ii. appx. ii.) that the abnormal values of the variation observed in the wood-built ships of his day was due to deviation of the compass caused by the iron in the ship; that the deviation was zero when the ship’s head was near the north and south points; that it attained its maximum on the east and west points, and varied as the sine of the azimuth of the ship’s head reckoned from the zero points. He also described a method of correcting deviation by means of a bar of vertical iron so placed as to correct the deviation nearly in all latitudes. This bar, now known as a “Flinders bar,” is still in general use. In 1820 Dr T. Young (see Brande’sQuarterly Journal, 1820) investigated mathematically the magnetism of ships. In 1824 Professor Peter Barlow (1776-1862) introduced his correcting plate ofsoftiron. Trials in certain ships showed that their magnetism consisted partly of hard iron, and the use of the plate was abandoned. In 1835 Captain E. J. Johnson, R.N., showed from experiments in the iron steamship “Garry Owen” that the vessel acted on an external compass as a magnet. In 1838 Sir G. B. Airy magnetically examined the iron steamship “Rainbow” at Deptford, and from his mathematical investigations (seePhil. Trans., 1839) deduced his method of correcting the compass by permanent magnets and soft iron, giving practical rules for the same in 1840. Airy’s and Flinders’s correctors form the basis of all compass correctors to this day. In 1838 S. D. Poisson published hisMemoir on the Deviations of the Compass caused by the Iron in a Vessel. In this he gave equations resulting from the hypothesis that the magnetism of a ship is partly due to the permanent magnetism of hard iron and partly to the transient induced magnetism of soft iron; that the latter is proportional to the intensity of the inducing force, and that the length of the needle is infinitesimally small compared to the distance of the surrounding iron. From Poisson’s equations Archibald Smith deduced the formulae given in theAdmiralty Manual for Deviations of the Compass(1st ed., 1862), a work which has formed the basis of numerous other manuals since published in Great Britain and other countries. In view of the serious difficulties connected with the inclining of every ship, Smith’s formulae for ascertaining and providing for the correction of the heeling error with the ship upright continue to be of great value to safe navigation. In 1855 the Liverpool Compass Committee began its work of investigating the magnetism of ships of the mercantile marine, resulting in three reports to the Board of Trade, all of great value, the last being presented in 1861.See alsoMagnetism, andNavigation; articles on Magnetism of Ships and Deviations of the Compass,Phil. Trans., 1839-1883,Journal United Service Inst., 1859-1889,Trans. Inst. Nav. Archit., 1860-1861-1862,Report of Brit. Assoc., 1862,London Quarterly Rev., 1865; alsoAdmiralty Manual, edit. 1862-1863-1869-1893-1900; and Towson’sPractical Information on Deviations of the Compass(1886).
The mariner’s compass during the early part of the 19th century was still a very imperfect instrument, although numerous inventors had tried to improve it. In 1837 the Admiralty Compass Committee was appointed to make a scientific investigation of the subject, and propose a form of compass suitable alike for azimuth and steering purposes. The committee reported in July 1840, and after minor improvements by the makers the admiralty compass, the card of which is shown in figs. 1 and 2, was adopted by the government. Until 1876, when Sir William Thomson introduced his patent compass, this compass was not only the regulation compass of the British navy, but was largely used in other countries in the same or a modified form. The introduction of powerful engines causing serious vibration to compass cards of the admiralty type, coupled with the prevailing desire for larger cards, the deviation of which could also be more conveniently compensated, led to the gradual introduction of the Thomson compass. Several important points were gained in the latter: the quadrantal deviation could be finally corrected for all latitudes; frictional error at the cap and pivot was reduced to a minimum, the average weight of the card being 200 grains; the long free vibrational period of the card was found to be favourable to its steadiness when the vessel was rolling. The first liquid compass used in England was invented by Francis Crow, of Faversham, in 1813. It is said that the idea of a liquid compass was suggested to Crow by the experience of the captain of a coasting vessel whose compass card was oscillating wildly until a sea broke on board filling the compass bowl, when the card became steady. Subsequent improvements were made by E. J. Dent, and especially by E. S. Ritchie, of Boston, Massachusetts. In 1888 the form of liquid compass (fig. 5) now solely used in torpedo boats and torpedo boat destroyers was introduced. It has also proved to be the most trustworthy compass under the shock of heavy gun fire at present available. The deflector is an instrument designed to enable an observer to reduce the deviations of the compass to an amount not exceeding 2° during fogs, or at any time when bearings of distant objects are not available. It is certain that if the directive forces on the north, east, south and west points of a compass are equal, there can be no deviation. With the deflector any inequality in the directive force can be detected, and hence the power of equalizing the forces by the usual soft iron and magnet correctors. Several kinds of deflector have been invented, that of Lord Kelvin (Sir William Thomson) being the simplest, but Dr Waghorn’s is also very effective. The use of the deflector is generally confined to experts.
The Magnetism of Ships.—In 1814 Flinders first showed (see Flinders’sVoyage, vol. ii. appx. ii.) that the abnormal values of the variation observed in the wood-built ships of his day was due to deviation of the compass caused by the iron in the ship; that the deviation was zero when the ship’s head was near the north and south points; that it attained its maximum on the east and west points, and varied as the sine of the azimuth of the ship’s head reckoned from the zero points. He also described a method of correcting deviation by means of a bar of vertical iron so placed as to correct the deviation nearly in all latitudes. This bar, now known as a “Flinders bar,” is still in general use. In 1820 Dr T. Young (see Brande’sQuarterly Journal, 1820) investigated mathematically the magnetism of ships. In 1824 Professor Peter Barlow (1776-1862) introduced his correcting plate ofsoftiron. Trials in certain ships showed that their magnetism consisted partly of hard iron, and the use of the plate was abandoned. In 1835 Captain E. J. Johnson, R.N., showed from experiments in the iron steamship “Garry Owen” that the vessel acted on an external compass as a magnet. In 1838 Sir G. B. Airy magnetically examined the iron steamship “Rainbow” at Deptford, and from his mathematical investigations (seePhil. Trans., 1839) deduced his method of correcting the compass by permanent magnets and soft iron, giving practical rules for the same in 1840. Airy’s and Flinders’s correctors form the basis of all compass correctors to this day. In 1838 S. D. Poisson published hisMemoir on the Deviations of the Compass caused by the Iron in a Vessel. In this he gave equations resulting from the hypothesis that the magnetism of a ship is partly due to the permanent magnetism of hard iron and partly to the transient induced magnetism of soft iron; that the latter is proportional to the intensity of the inducing force, and that the length of the needle is infinitesimally small compared to the distance of the surrounding iron. From Poisson’s equations Archibald Smith deduced the formulae given in theAdmiralty Manual for Deviations of the Compass(1st ed., 1862), a work which has formed the basis of numerous other manuals since published in Great Britain and other countries. In view of the serious difficulties connected with the inclining of every ship, Smith’s formulae for ascertaining and providing for the correction of the heeling error with the ship upright continue to be of great value to safe navigation. In 1855 the Liverpool Compass Committee began its work of investigating the magnetism of ships of the mercantile marine, resulting in three reports to the Board of Trade, all of great value, the last being presented in 1861.
See alsoMagnetism, andNavigation; articles on Magnetism of Ships and Deviations of the Compass,Phil. Trans., 1839-1883,Journal United Service Inst., 1859-1889,Trans. Inst. Nav. Archit., 1860-1861-1862,Report of Brit. Assoc., 1862,London Quarterly Rev., 1865; alsoAdmiralty Manual, edit. 1862-1863-1869-1893-1900; and Towson’sPractical Information on Deviations of the Compass(1886).
(E. W. C.)
History of the Mariner’s Compass.
The discovery that a lodestone, or a piece of iron which has been touched by a lodestone, will direct itself to point in a north and south position, and the application of that discovery to direct the navigation of ships, have been attributed to various origins. The Chinese, the Arabs, the Greeks, the Etruscans, the Finns and the Italians have all been claimed as originators of the compass. There is now little doubt that the claim formerly advanced in favour of the Chinese is ill-founded. In Chinese history we are told how, in the sixty-fourth year of the reign of Hwang-ti (2634B.C.), the emperor Hiuan-yuan, or Hwang-ti, attacked one Tchi-yeou, on the plains of Tchou-lou, and finding his army embarrassed by a thick fog raised by the enemy, constructed a chariot (Tchi-nan) for indicating the south, so as to distinguish the four cardinal points, and was thus enabled to pursue Tchi-yeou, and take him prisoner. (Julius Klaproth,Lettre à M. le Baron Humboldt sur l’invention de la boussole, Paris, 1834. See also Mailla,Histoire générale de la Chine, tom. i. p. 316, Paris, 1777.) But, as other versions of the story show, this account is purely mythical. For the south-pointing chariots are recorded to have been first devised by the emperor Hian-tsoung (A.D.806-820); and there is no evidence that they contained any magnet. There is no genuine record of a Chinese marine compass beforeA.D.1297, as Klaproth admits. No sea-going ships were built in China before 139B.C.The earliest allusion to the power of the lodestone in Chinese literature occurs in a Chinese dictionary, finished inA.D.121, where the lodestone is defined as “a stone with which an attraction can be given to a needle,” but this knowledge is no more than that existing in Europe at least five hundred years before. Nor is there any nautical significance in a passage which occurs in the Chinese encyclopaedia,Poei-wen-yun-fou, in which it is stated that under the Tsin dynasty, or betweenA.D.265 and 419, “there were ships indicating the south.”
The Chinese, Sir J. F. Davis informs us, once navigated as far as India, but their most distant voyages at present extend not farther than Java and the Malay Islands to the south (The Chinese, vol. iii. p. 14, London, 1844). According to an Arabic manuscript, a translation of which was published by Eusebius Renaudot (Paris, 1718), they traded in ships to the Persian Gulfand Red Sea in the 9th century. Sir G. L. Staunton, in vol. i. of hisEmbassy to China(London, 1797), after referring to the early acquaintance of the Chinese with the property of the magnet to point southwards, remarks (p. 445), “The nature and the cause of the qualities of the magnet have at all times been subjects of contemplation among the Chinese. The Chinese name for the compass isting-nan-ching, or needle pointing to the south; and a distinguishing mark is fixed on the magnet’s southern pole, as in European compasses upon the northern one.” “The sphere of Chinese navigation,” he tells us (p. 447), “is too limited to have afforded experience and observation for forming any system of laws supposed to govern the variation of the needle.... The Chinese had soon occasion to perceive how much more essential the perfection of the compass was to the superior navigators of Europe than to themselves, as the commanders of the ‘Lion’ and ‘Hindostan,’ trusting to that instrument, stood out directly from the land into the sea.” The number of points of the compass, according to the Chinese, is twenty-four, which are reckoned from the south pole; the form also of the instrument they employ is different from that familiar to Europeans. The needle is peculiarly poised, with its point of suspension a little below its centre of gravity, and is exceedingly sensitive; it is seldom more than an inch in length, and is less than a line in thickness. “It may be urged,” writes Mr T. S. Davies, “that the different manner of constructing the needle amongst the Chinese and European navigators shows the independence of the Chinese of us, as theirs is the worse method, and had they copied from us, they would have used the better one” (Thomson’sBritish Annual, 1837, p. 291). On the other hand, it has been contended that a knowledge of the mariner’s compass was communicated by them directly or indirectly to the early Arabs, and through the latter was introduced into Europe. Sismondi has remarked (Literature of Europe, vol. i.) that it is peculiarly characteristic of all the pretended discoveries of the middle ages that when the historians mention them for the first time they treat them as things in general use. Gunpowder, the compass, the Arabic numerals and paper, are nowhere spoken of as discoveries, and yet they must have wrought a total change in war, in navigation, in science, and in education. G. Tiraboschi (Storia della letteratura italiana, tom. iv. lib. ii. p. 204, et seq., ed. 2., 1788), in support of the conjecture that the compass was introduced into Europe by the Arabs, adduces their superiority in scientific learning and their early skill in navigation. He quotes a passage on the polarity of the lodestone from a treatise translated by Albertus Magnus, attributed by the latter to Aristotle, but apparently only an Arabic compilation from the works of various philosophers. As the termsZoronandAphron, used there to signify the south and north poles, are neither Latin nor Greek, Tiraboschi suggests that they may be of Arabian origin, and that the whole passage concerning the lodestone may have been added to the original treatise by the Arabian translators.
Dr W. Robertson asserts (Historical Disquisition concerning Ancient India, p. 227) that the Arabs, Turks and Persians have no original name for the compass, it being called by themBossola, the Italian name, which shows that the thing signified is foreign to them as well as the word. The Rev. G. P. Badger has, however, pointed out (Travels of Ludovico di Varthema, trans. J. W. Jones, ed. G. P. Badger, Hakluyt Soc, 1863, note, pp. 31 and 32) that the name of Bushla or Busba, from the ItalianBussola, though common among Arab sailors in the Mediterranean, is very seldom used in the Eastern seas,—DaïrahandBeit el-Ibrah(the Circle, or House of the Needle) being the ordinary appellatives in the Red Sea, whilst in the Persian GulfKiblah-nāmehis in more general use. Robertson quotes Sir J. Chardin as boldly asserting “that the Asiatics are beholden to us for this wonderful instrument, which they had from Europe a long time before the Portuguese conquests. For, first, their compasses are exactly like ours, and they buy them of Europeans as much as they can, scarce daring to meddle with their needles themselves. Secondly, it is certain that the old navigators only coasted it along, which I impute to their want of this instrument to guide and instruct them in the middle of the ocean.... I have nothing but argument to offer touching this matter, having never met with any person in Persia or the Indies to inform me when the compass was first known among them, though I made inquiry of the most learned men in both countries. I have sailed from the Indies to Persia in Indian ships, when no European has been aboard but myself. The pilots were all Indians, and they used the forestaff and quadrant for their observations. These instruments they have from us, and made by our artists, and they do not in the least vary from ours, except that the characters are Arabic. The Arabs are the most skilful navigators of all the Asiatics or Africans; but neither they nor the Indians make use of charts, and they do not much want them; some they have, but they are copied from ours, for they are altogether ignorant of perspective.” The observations of Chardin, who flourished between 1643 and 1713, cannot be said to receive support from the testimony of some earlier authorities. That the Arabs must have been acquainted with the compass, and with the construction and use of charts, at a period nearly two centuries previous to Chardin’s first voyage to the East, may be gathered from the description given by Barros of a map of all the coast of India, shown to Vasco da Gama by a Moor of Guzerat (about the 15th of July 1498), in which the bearings were laid down “after the manner of the Moors,” or “with meridians and parallels very small (or close together), without other bearings of the compass; because, as the squares of these meridians and parallels were very small, the coast was laid down by these two bearings of N. and S., and E. and W., with great certainty, without that multiplication of bearings of the points of the compass usual in our maps, which serves as the root of the others.” Further, we learn from Osorio that the Arabs at the time of Gama “were instructed in so many of the arts of navigation, that they did not yield much to the Portuguese mariners in the science and practice of maritime matters.” (SeeThe Three Voyages of Vasco da Gama, Hakluyt Soc, 1869; note to chap. xv. by the Hon. H. E. J. Stanley, p. 138.) Also the Arabs that navigated the Red Sea at the same period are shown by Varthema to have used the mariner’s chart and compass (Travels, p. 31).
Again, it appears that compasses of a primitive description, which can hardly be supposed to have been brought from Europe, were employed in the East Indies certainly as early as several years previous to the close of the 16th century. In William Barlowe’sNavigator’s Supply, published in 1597, we read:—“Some fewe yeeres since, it so fell out that I had severall conferences with two East Indians which were brought into England by master Candish [Thomas Cavendish], and had learned our language: The one of them was of Mamillia [Manila] in the Isle of Luzon, the other of Miaco in Japan. I questioned with them concerning their shipping and manner of sayling. They described all things farre different from ours, and shewed, that in steade of our Compas, they use a magneticall needle of sixe ynches long, and longer, upon a pinne in a dish of whiteChinaearth filled with water; In the bottome whereof they have two crosse lines, for the foure principall windes; the rest of the divisions being reserved to the skill of their Pilots.” Bailak Kibdjaki, also, an Arabian writer, shows in hisMerchant’s Treasure, a work given to the world in 1282, that the magnetized needle, floated on water by means of a splinter of wood or a reed, was employed on the Syrian seas at the time of his voyage from Tripoli to Alexandria (1242), and adds:—“They say that the captains who navigate the Indian seas use, instead of the needle and splinter, a sort of fish made out of hollow iron, which, when thrown into the water, swims upon the surface, and points out the north and south with its head and tail” (Klaproth,Lettre, p. 57). E. Wiedemann, inErlangen Sitzungsberichte(1904, p. 330), translates the phrase given above as splinter of wood, by the term wooden cross. Furthermore, although the sailors in the Indian vessels in which Niccola de’ Conti traversed the Indian seas in 1420 are stated to have had no compass, still, on board the ship in which Varthema, less than a century later, sailed from Borneo to Java, both the mariner’s chart and compass were used; it has been questioned, however, whether in this case the compass was ofEastern manufacture (Travels of Varthema, Introd. xciv, and p. 249). We have already seen that the Chinese as late as the end of the 18th century made voyages with compasses on which but little reliance could be placed; and it may perhaps be assumed that the compasses early used in the East were mostly too imperfect to be of much assistance to navigators, and were therefore often dispensed with on customary routes. The Arab traders in the Levant certainly used a floating compass, as did the Italians before the introduction of the pivoted needle; the magnetized piece of iron being floated upon a small raft of cork or reeds in a bowl of water. The Italian name ofcalamita, which still persists, for the magnet, and which literally signifies a frog, is doubtless derived from this practice.
The simple water-compass is said to have been used by the Coreans so late as the middle of the 18th century; and Dr T. Smith, writing in thePhilosophical Transactionsfor 1683-1684, says of the Turks (p. 439), “They have no genius for Sea-voyages, and consequently are very raw and unexperienced in the art of Navigation, scarce venturing to sail out of sight of land. I speak of the naturalTurks, who trade either into theblack Seaor some part of theMorea, or betweenConstantinopleandAlexandria, and not of the Pyrats ofBarbary, who are for the most part Renegado’s, and learnt their skill in Christendom. ... The Turkish compass consists but of 8 points, the four Cardinal and the four Collateral.” That the value of the compass was thus, even in the latter part of the 17th century, so imperfectly recognized in the East may serve to explain how in earlier times that instrument, long after the first discovery of its properties, may have been generally neglected by navigators.
The Arabic geographer, Edrisi, who lived about 1100, is said by Boucher to give an account, though in a confused manner, of the polarity of the magnet (Hallam,Mid. Ages, vol. iii. chap. 9, part 2); but the earliest definite mention as yet known of the use of the mariner’s compass in the middle ages occurs in a treatise entitledDe utensilibus, written by Alexander Neckam in the 12th century. He speaks there of a needle carried on board ship which, being placed on a pivot, and allowed to take its own position of repose, shows mariners their course when the polar star is hidden. In another work,De naturis rerum, lib. ii. c. 89, he writes,—“Mariners at sea, when, through cloudy weather in the day which hides the sun, or through the darkness of the night, they lose the knowledge of the quarter of the world to which they are sailing, touch a needle with the magnet, which will turn round till, on its motion ceasing, its point will be directed towards the north” (W. Chappell,Nature, No. 346, June 15, 1876). The magnetical needle, and its suspension on a stick or straw in water, are clearly described inLa Bible Guiot, a poem probably of the 13th century, by Guiot de Provins, wherein we are told that through the magnet (la manetteorl’amanière), an ugly brown stone to which iron turns of its own accord, mariners possess an art that cannot fail them. A needle touched by it, and floated by a stick on water, turns its point towards the pole-star, and a light being placed near the needle on dark nights, the proper course is known (Hist. littéraire de la France, tom. ix. p. 199; Barbazan,Fabliaux, tom. ii. p. 328). Cardinal Jacques de Vitry, bishop of Acon in Palestine, in hisHistory(cap. 89), written about the year 1218, speaks of the magnetic needle as “most necessary for such as sail the sea”;1and another French crusader, his contemporary, Vincent de Beauvais, states that the adamant (lodestone) is found in Arabia, and mentions a method of using a needle magnetized by it which is similar to that described by Kibdjaki. In 1248 Hugo de Bercy notes a change in the construction of compasses, which are now supported on two floats in a glass cup. From quotations given by Antonio Capmany (Questiones Criticas) from theDe contemplationeof Raimon Lull, of the date 1272, it appears that the latter was well acquainted with the use of the magnet at sea;2and before the middle of the 13th century Gauthier d’Espinois alludes to its polarity, as if generally known, in the lines:—
“Tous autresi comme l’aimant decoit [detourne]L’aiguillette par force de vertu,A ma dame tor le mont [monde] retenueQui sa beauté connoit et aperçoit.”
“Tous autresi comme l’aimant decoit [detourne]
L’aiguillette par force de vertu,
A ma dame tor le mont [monde] retenue
Qui sa beauté connoit et aperçoit.”
Guido Guinizzelli, a poet of the same period, writes:—“In those parts under the north are the mountains of lodestone, which give the virtue to the air of attracting iron; but because it [the lodestone] is far off, [it] wishes to have the help of a similar stone to make it [the virtue] work, and to direct the needle towards the star.”3Brunetto Latini also makes reference to the compass in his encyclopaediaLivres dou trésor, composed about 1260 (Livre i. pt. ii. ch. cxx.):—“Por ce nagent li marinier à l’enseigne des estoiles qui i sont, que il apelent tramontaines, et les gens qui sont en Europe et es parties decà nagent à la tramontaine de septentrion, et li autre nagent à cele de midi. Et qui n’en set la verité, praigne une pierre d’aimant, et troverez que ele a ij faces: l’une qui gist vers l’une tramontaine, et l’autre gist vers l’autre. Et à chascune des ij faces la pointe d’une aguille vers cele tramontaine à cui cele face gist. Et por ce seroient li marinier deceu se il ne se preissent garde” (p. 147, Paris edition, 1863). Dante (Paradiso, xii. 28-30) mentions the pointing of the magnetic needle toward the pole star. In Scandinavian records there is a reference to the nautical use of the magnet in theHauksbók, the last edition of theLandnámabók(Book of the Colonization of Iceland):—“Floki, son of Vilgerd, instituted a great sacrifice, and consecrated three ravens which should show him the way (to Iceland); for at that time no men sailing the high seas had lodestones up in northern lands.”
Haukr Erlendsson, who wrote this paragraph about 1300, died in 1334; his edition was founded on material in two earlier works, that of Styrmir Karason (who died 1245), which is lost, and that of Hurla Thordson (died 1284) which has no such paragraph. All that is certain is a knowledge of the nautical use of the magnet at the end of the 13th century. From T. Torfaeus we learn that the compass, fitted into a box, was already in use among the Norwegians about the middle of the 13th century (Hist. rer. Norvegicarum, iv. c. 4, p. 345, Hafniae, 1711); and it is probable that the use of the magnet at sea was known in Scotland at or shortly subsequent to that time, though King Robert, in crossing from Arran to Carrick in 1306, as Barbour writing in 1375 informs us, “na nedill had na stane,” but steered by a fire on the shore. Roger Bacon (Opus majusandOpus minus, 1266-1267) was acquainted with the properties of the lodestone, and wrote that if set so that it can turn freely (swimming on water) it points toward the poles; but he stated that this was not due to the pole-star, but to the influence of the northern region of the heavens.
The earliest unquestionable description of a pivoted compass is that contained in the remarkableEpistola de magneteof Petrus Peregrinus de Maricourt, written at Lucera in 1269 to Sigerus de Foncaucourt. (First printed edition Augsburg, 1558. See also Bertelli in Boncompagni’sBollettino di bibliografia, t. i., or S. P. Thompson inProc. British Academy, vol. ii.) Of this work twenty-eight MSS. exist; seven of them being at Oxford. The first part of the epistle deals generally with magnetic attractions and repulsions, with the polarity of the stone, and with the supposed influence of the poles of the heavens upon the poles of the stone. In the second part Peregrinus describes first an improved floating compass with fiducial line, a circle graduated with 90 degrees to each quadrant, and provided with movable sights for taking bearings. He then describes a new compass with a needle thrust through a pivoted axis, placed in a box with transparent cover, cross index of brass or silver, divided circle, and an external “rule” or alhidade provided with a pair of sights. In the Leiden MS. of this work, which for long was erroneously ascribed to one Peter Adsiger, is a spurious passage, long believed to mention the variation of the compass.
Prior to this clear description of a pivoted compass by Peregrinus in 1269, the Italian sailors had used the floating magnet, probably introduced into this region of the Mediterranean by traders belonging to the port of Amalfi, as commemorated in the line of the poet Panormita:—
“Prima dedit nautis usum magnetis Amalphis.”
This opinion is supported by the historian Flavius Blondus in hisItalia illustrata, written about 1450, who adds that its certain origin is unknown. In 1511 Baptista Pio in hisCommentaryrepeats the opinion as to the invention of the use of the magnet at Amalfi as related by Flavius. Gyraldus, writing in 1540 (Libellus de re nautica), misunderstanding this reference, declared that this observation of the direction of the magnet to the poles had been handed down as discovered “by a certain Flavius.” From this passage arose a legend, which took shape only in the 17th century, that the compass was invented in the year 1302 by a person to whom was given the fictitious name of Flavio Gioja, of Amalfi.
From the above it will have been evident that, as Barlowe remarks concerning the compass, “the lame tale of one Flavius at Amelphus, in the kingdome of Naples, for to have devised it, is of very slender probabilitie”; and as regards the assertion of Dr Gilbert, of Colchester (De magnete, p. 4, 1600), that Marco Polo introduced the compass into Italy from the East in 1260,4we need only quote the words of Sir H. Yule (Book of Marco Polo):—“Respecting the mariner’s compass and gunpowder, I shall say nothing, as no one now, I believe, imagines Marco to have had anything to do with their introduction.”
When, and by whom, the compass card was added is a matter of conjecture. Certainly theRosa Ventorum, orWind-rose, is far older than the compass itself; and the naming of the eight principal “winds” goes back to the Temple of the Winds in Athens built by Andronicus Cyrrhestes. The earliest known wind-roses on theportulanior sailing charts of the Mediterranean pilots have almost invariably the eight principal points marked with the initials of the principal winds, Tramontano, Greco, Levante, Scirocco, Ostro, Africo (or Libeccio), Ponente and Maestro, or with a cross instead of L, to mark the east point. The north point, indicated in some of the oldest compass cards with a broad arrow-head or a spear, as well as with a T for Tramontano, gradually developed by a combination of these, about 1492, into afleur de lis, still universal. The cross at the east continued even in British compasses till about 1700. Wind-roses with these characteristics are found in Venetian and Genoese charts of early 14th century, and are depicted similarly by the Spanish navigators. The naming of the intermediate subdivisions making up the thirty-two points or rhumbs of the compass card is probably due to Flemish navigators; but they were recognized even in the time of Chaucer, who in 1391 wrote, “Now is thin Orisonte departed in xxiiii partiez by thi azymutz, in significacion of xxiiii partiez of the world: al be it so that ship men rikne thilke partiez in xxxii” (Treatise on the Astrolabe, ed. Skeat, Early English Text Soc., London, 1872). The mounting of the card upon the needle or “flie,” so as to turn with it, is probably of Amalphian origin. Da Buti, the Dante commentator, in 1380 says the sailors use a compass at the middle of which is pivoted a wheel of light paper to turn on its pivot, on which wheel the needle is fixed and the star (wind-rose) painted. The placing of the card at the bottom of the box, fixed, below the needle, was practised by the compass-makers of Nuremberg in the 16th century, and by Stevinus of Bruges about 1600. The gimbals or rings for suspension hinged at right-angles to one another, have been erroneously attributed to Cardan, the proper term beingcardine, that is hinged or pivoted. The earliest description of them is about 1604. The termbinnacle, originallybittacle, is a corruption of the Portuguese abitacolo, to denote the housing enclosing the compass, probably originating with the Portuguese navigators.
The improvement of the compass has been but a slow process.The Libel of English Policie, a poem of the first half of the 15th century, says with reference to Iceland (chap. x.)—
“Out of Bristowe, and costes many one,Men haue practised by nedle and by stoneThider wardes within a litle while.”Hakluyt,Principal Navigations, p. 201 (London, 1599).
“Out of Bristowe, and costes many one,
Men haue practised by nedle and by stone
Thider wardes within a litle while.”
Hakluyt,Principal Navigations, p. 201 (London, 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 treatiseMagnetical 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 Peter Barlow reported to the Admiralty that half the compasses in the British Navy were mere lumber and ought to be destroyed. He introduced a pattern having four or five parallel straight strips of magnetized steel fixed under a card, a form which remained the standard admiralty type until the introduction of the modern Thomson (Kelvin) compass in 1876.
(F. H. B.; S. P. T.)
1Adamas in India reperitur ... Ferrum occulta quadam natura ad se trahit. Acus ferrea postquam adamantem contigerit, ad stellam septentrionalem ... semper convertitur, unde valde necessarius est navigantibus in mari.2Sicut acus per naturam vertitur ad septentrionem dum sit tacta a magnete.—Sicut acus nautica dirigit marinarios in sua navigatione.3Ginguené,Hist. lit. de l’Italie, t. i. p. 413.4“According to all the texts he returned to Venice in 1295 or, as is more probable, in 1296.”—Yule.
1Adamas in India reperitur ... Ferrum occulta quadam natura ad se trahit. Acus ferrea postquam adamantem contigerit, ad stellam septentrionalem ... semper convertitur, unde valde necessarius est navigantibus in mari.
2Sicut acus per naturam vertitur ad septentrionem dum sit tacta a magnete.—Sicut acus nautica dirigit marinarios in sua navigatione.
3Ginguené,Hist. lit. de l’Italie, t. i. p. 413.
4“According to all the texts he returned to Venice in 1295 or, as is more probable, in 1296.”—Yule.
COMPASS PLANT,a native of the North American prairies, which takes its name from the position assumed by the leaves. These turn their edges to north and south, thus avoiding the excessive mid-day heat, while getting the full benefit of the morning and evening rays. The plant is known botanically asSilphium laciniatum, and belongs to the natural order Compositae. Another member of the same order,Lactuca Scariola, which has been regarded as the origin of the cultivated lettuce (L. sativa), behaves in the same way when growing in dry exposed places; it is a native of Europe and northern Asia which has got introduced into North America.
COMPAYRE, JULES GABRIEL(1843- ), French educationalist, was born at Albi. He entered the École Normale Supérieure in 1862 and became professor of philosophy. In 1876 he was appointed professor in the Faculty of Letters of Toulouse, and upon the creation of the École normale d’institutrices at Fontenay aux Roses he became teacher of pedagogy (1880). From 1881 to 1889 he was deputy for Lavaur in the chamber, and took an active part in the discussions on public education. Defeated at the elections of 1889, he was appointed rector of the academy of Poitiers in 1890, and five years later to the academy of Lyons. His principal publications are hisHistoire critique des doctrines de l’éducation en France(1879);Éléments d’éducation civique(1881), a work placed on the index at Rome, but very widely read in the primary schools of France;Cours de pédagogie théorique et pratique(1885, 13th ed., 1897);The Intellectual and Moral Development of the Child, in English (2 vols., New York, 1896-1902); and a series of monographs onLes Grands Éducateurs.
COMPENSATION(from Lat.compensare, to weigh one thing against another), a term applied in English law to a number of different forms of legal reparation;e.g.under the Forfeiture Act 1870 (s. 4), for loss of property caused by felony, or—under the Riot (Damages) Act 1886—to persons whose property has been stolen, destroyed or injured by rioters (seeRiot). It is due, under the Agricultural Holdings Acts 1883-1906, for agricultural improvements (seeLandlord and Tenant; cf. alsoAllotments and Small Holdings), and under the Workmen’s Compensation Act 1906 to workmen, in respect of accidents in the course of their employment (seeEmployers’ Liability); and under the Licensing Act 1904, to the payments to be made on the extinction of licences to sell intoxicants. The term“Compensation water” is used to describe the water given from a reservoir in compensation for water abstracted from a stream, under statutory powers, in connexion with public works (seeWater Supply). As to the use of the word “compensation” in horology, seeClock;Watch.
Compensation, in its most familiar sense, is however anomen jurisfor the reparation or satisfaction made to the owners of property which is taken by the state or by local authorities or by the promoters of parliamentary undertakings, under statutory authority, for public purposes. There are two main legal theories on which such appropriation of private property is justified. The American may be taken as a representative illustration of the one, and the English of the other. Though not included in the definition of “eminent domain,” the necessity for compensation is recognized as incidental to that power. (SeeEminent Domain, under which the American law of compensation, and the closely allied doctrine ofexpropriation pour cause d’utilitépublique of French law, and the law of other continental countries, are discussed.) The rule of English constitutional law, on the other hand, is that the property of the citizen cannot be seized for purposes which are really “public” without a fair pecuniary equivalent being given to him; and, as the money for such compensation must come from parliament, the practical result is that the seizure can only be effected under legislative authority. An action for illegal interference with the property of the subject is not maintainable against officials of the crown or government sued in their official capacity or as an official body. But crown officials may be sued in their individual capacity for such interference, even if they acted with the authority of the government (cp.Raleighv.Goschen[1898], 1 Ch. 73).
Law of England.—Down to 1845 every act authorizing the purchase of lands had, in addition to a number of common form clauses, a variety of special clauses framed with a view to meeting the particular circumstances with which it dealt. In 1845, however, a statute based on the recommendations of a select committee, appointed in the preceding year, was passed; the object being to diminish the bulk of the special acts, and to introduce uniformity into private bill legislation by classifying the common form clauses, embodying them in general statutes, and facilitating their incorporation into the special statutes by reference. The statute by which this change was initiated was the Lands Clauses Consolidation Act 1845; and the policy has been continued by a series of later statutes which, together with the act of 1845, are now grouped under the generic title of the Lands Clauses Acts.
The public purposes for which lands are taken are threefold. Certain public departments, such as the war office and the admiralty, may acquire lands for national purposes (see the Defence Acts 1842 to 1873; and the Lands Clauses Consolidation Act 1860, s. 7). Local authorities are enabled to exercise similar powers for an enormous variety of municipal purposes,e.g.the housing of the working classes, the improvement of towns, and elementary and secondary education. Lastly, the promoters of public undertakings of a commercial character, such as railways and harbours, carry on their operations under statutes in which the provisions of the Lands Clauses Acts are incorporated.
Lands may be taken under the Lands Clauses Acts either by agreement or compulsorily. The first step in the proceedings is a “notice to treat,” or intimation by the promoters of their readiness to purchase the land, coupled with a demand for particulars as to the estate and the interests in it. The landowner on whom the notice is served may meet it by agreeing to sell, and the terms may then be settled by consent of the parties themselves, or by arbitration, if they decide to have recourse to that mode of adjusting the difficulty. If the property claimed is a house, or other building or manufactory, the owner has a statutory right to require the promoters by a counternotice to take the whole, even although a part would serve their purpose. This rule, however, is, in modern acts, often modified by special clauses. On receipt of the counter-notice the promoters must either assent to the requirement contained in it, or abandon their notice to treat. On the other hand, if the landowner fails within twenty-one days after receipt of the notice to treat to give the particulars which it requires, the promoters may proceed to exercise their compulsory powers and to obtain assessment of the compensation to be paid. As a general rule, it is a condition precedent to the exercise of these powers by a company that the capital of the undertaking should be fully subscribed. Compensation, under the Lands Clauses Acts, is assessed in four different modes:—(1) by justices, where the claim does not exceed £50, or a claimant who has no greater interest than that of a tenant for a year, or from year to year, is required to give up possession before the expiration of his tenancy; (2) by arbitration (a) when the claim exceeds £50, and the claimant desires arbitration, and the interest is not a yearly tenancy, (b) when the amount has been ascertained by a surveyor, and the claimant is dissatisfied, (c) when superfluous lands are to be sold, and the parties entitled to pre-emption and the promoters cannot agree as to the price. (Lands become “superfluous” if taken compulsorily on an erroneous estimate of the area needed, or if part only was needed and the owner compelled the promoters under the power above mentioned to take the whole, or in cases of abandonment); (3) by a jury, when the claim exceeds £50, and (a) the claimant does not signify his desire for arbitration, or no award has been made within the prescribed time, or (b) the claimant applies in writing for trial by jury; (4) by surveyors, nominated by justices, where the owner is under disability, or does not appear at the appointed time, or the claim is in respect of commonable rights, and a committee has not been appointed to treat with the promoters.
Promoters are not allowed without the consent of the owner to enter upon lands which are the subject of proceedings under the Lands Clauses Acts, except for the purpose of making a survey, unless they have executed a statutory bond and made a deposit, at the Law Courts Branch of the Bank of England, as security for the performance of the conditions of the bond.
Measure of Value.—(1) Where land is taken, the basis on which compensation is assessed is the commercial value of the land to the owner at the date of the notice to treat. Potential value may be taken into account, and also good-will of the property in a business. This rule, however, excludes any consideration of the principle of “betterment.” (2) Where land, although not taken, is “injuriously affected” by the works of the promoters, compensation is payable for loss or damage resulting from any act, legalized by the promoters’ statutory powers, which would otherwise have been actionable, or caused by the execution (not the use) of the works authorized by the undertaking.
The following examples of how land may be “injuriously affected,” so as to give a right to compensation under the acts, may be given:—narrowing or obstructing a highway which is the nearest access to the lands in question; interference with a right of way; substantial interference with ancient lights; noise of children outside a board school.
Scotland and Ireland.—The Lands Clauses Act 1845 extends to Ireland. There is a Scots enactment similar in character (Lands Clauses [Scotland] Act 1845). The principles and practice of the law of compensation are substantially the same throughout the United Kingdom.
India and the British Colonies.—Legislation analogous to the Lands Clauses Acts is in force in India (Land Acquisition Act 1894 [Act I of 1894]) and in most of the colonies (see western Australia, Lands Resumption Act 1894 [58 Vict. No. 33], Victoria, Lands Compensation Act 1890 [54 Vict. No. 1109]; New Zealand, Public Works Act 1894 [58 Vict. No. 42]; Ontario [Revised Stats. 1897, c. 37]).