In 1787, a royal observatory was constructed at the Chateau de St. George, in Lisbon, which was superintended by M. Custodio Gomez. There is also one at Coimbra, which contains a fine equatorial by Troughton. At Petersburg an observatory was built, in 1725, by the czar Peter, who showed great zeal for science in general, and particularly for astronomy. When he was in England, some years before that period, he visited the Royal Observatory at Greenwich, where he examined both the building and the instruments with very great attention. The observatory which he afterwards built is one of the most magnificent in Europe. It is 130 feet high, with three stories, all fit for astronomical purposes. M. Delisle has made, according to Lalande, a great number of excellent observations here, which are preserved in manuscript in the marine depôt. At Moscow an observatory was built a few years ago, and furnished with some excellent English instruments, chiefly by Cary; but it is probable that they have been destroyed in the late conflagration of that city. In Italy, practical astronomy has been cultivated with much assiduity and success during the last century, chiefly by ecclesiastics, and particularly by the Jesuits. At Rome, cardinal Zelada constructed, at his own expense, on the southern part of the Roman college, a very fine observatory, with the large sector of father Boscovich, and other instruments by Ramsden and Dollond. The abbé Calandrelli observed here with great attention and accuracy for many years. Other buildings of a similar description have been erected in different parts of Rome. At Bologna a magnificent observatory was built in 1714, in the palace of the Institute, by the munificence of the celebrated count Marsigli; and pope Benedict 14 gave afterwards a large sum of money towards the purchase of instruments. Here a succession of able astronomers have observed, among whom may be mentioned Manfredi, Zanotti, Canterzani, &c. At Pisa the observatory is in the form of a tower. It was built in 1730, at the expense of the university, and supplied with superb apparatus made by Sisson, Short, Graham, &c. Perelli observed here for many years, and had for a successor M. Slope, who published an excellent collection of observations in 1789. At Milan there is an observatory, which is reckoned one of the most useful in Italy. It was built in 1765, at the cost of the college of the Jesuits, chiefly through the zeal of father Pallavicini, and under the direction of father Boscovich, who also contributed liberally to the expense. The instruments have been made with great care by the principal French and English artists. Among the observers may be also mentioned Reggio, Oriani, and Cesaris. At Florence, father Ximenes erected an observatory at the college of Jesuits, which contains a quadrant by Toscanelli, larger than any other known, with which he made observations to prove the secular diminution of the obliquity of the ecliptic. At his death he bequeathed the whole to the college. In 1772 the grand duke Leopold built an observatory, which M. Fontana superintended, and in 1786 several fine instruments by Ramsden were added ..to it. Panigai, and a small one near the town by M. Miotti. One was also built at Parma by father Belgrado, and another at Brescia by father Cavalli. At Verona, Cagnoli, eminent both as a mathematician and astronomer, erected an observatory at his own expense, in 1787, and placed in it the best instruments, with which he has made very accurate and important observations, particularly on the precession of the equinoxes, and on the places of 473 northern stars, and 28 southern, of which he has made a catalogue. In these determinations he has been perhaps more attentive than any other astronomer to the minute changes of refraction, and to the aberration of light. At Padua there is an observatory, which in 1778 was furnished with instruments, chiefly made by Ramsden. It has been many years under the direction of M. Toaldo, who has published several useful works, especially a treatise on meteorology, which gained him the prize at the academy of Montpellier. In some of the islands of the Mediterranean observatories have also been established. We shall, however, notice only those of Malta and Sicily. In 1783, the grand-master Emmanuel de Rohan, an amateur and enlightened protector of science, invited to Malta chevalier d'Angos, a skilful astronomer, who converted a tower of the palace into an observatory, which was furnished with the finest instruments that could be procured. In a few years he made a great number of valuable observations, which he intended to publish, but in March 1789, the observatory having caught fire, the instruments were broken, and the papers burnt, a serious loss to astronomy, particularly as this was the most southern observatory of Europe, in latitude 36°. At Palermo an observatory was constructed in the palace of the viceroy, under the direction of father Piazzi, who went to Paris in 1787 to study astronomy, and who afterwards visited England, in order to consult the principal artists on the construction of instruments. In 1789 he returned to Palermo, and added to the apparatus a fine transit instrument, and a complete circle, made by Ramsden. His first labours were directed to the formation of a correct catalogue of stars, and, as a foundation, he chose Wollaston's catalogue, and particularly, as his chief points of reference, Dr. Maskelyne's 36 stars. The positions of some of the larger stars he verified by nearly a hundred observations, and in the prosecution of this task, in 1801, he discovered a new planet, which he named Ceres, in honour of Sicily, as that island was, on account of its fertility, anciently consecrated to the goddess Ceres. This discovery was the more important, as it excited the curiosity and research of other astronomers, by which three more planets have been since discovered. English Observatories. The Greenwich Observatory, or the Royal Observatory of England, was built and endowed by King Charles 11, who, to use the words of Bailly, "well knew how essential astronomy was to a maritime and commercial people like the English, who aspired to the empire of the seas." This building was erected on the site of the ancient moated tower of Duke Humphrey, uncle to Henry 6, and the first stone of it was laid Aug. 10, 1675, by Mr. Flam steed, who had been appointed astronomer-royal. It is situated on the highest eminence of Greenwich park, about 160 feet above low-water mark. The soil here is particularly favourable for such an institution, being of a Ainty gravel, through which the rain soon passes, and thus the atmosphere is generally dry, which contributes to the preservation of the instruments, as well as to the uniformity of refraction. This establishment comprehends two principal buildings, one of which is the observatory, and the other the dwelling-house of the astronomer-royal. The observatory is an oblong edifice, running east and west, and containing four rooms or apartments on the ground-floor. The first, or most easterly room, has been lately erected for the reception and fitting up of a very fine transit circle, by Troughton, and a clock of great value by Hardy. The next apartment is the transit room. It has a double sloping roof, with sliding shutters, which are opened both north and south, with great ease, by pulleys. The transit instrument, which is 8 feet long, and the axis 3 feet, is suspended on two stone pillars. This instrument is famous as having been used by Halley, Bradley, and Maskelyne. It was originally made by Bird, and has been successively improved by Dollond and Troughton. The astronomical or transit clock, which is attached to a stone pillar, was made by Graham, and has been rendered very accurate by Earnshaw. The third apartment is the assistant observer's library and place for calculation; and the western apartment of the building is the quadrant room. Here is erected a stone pier, running north and south, to which are attached two mural quadrants, each of 8 feet radius. That on the eastern face, which observes the southern meridian, was made by Bird, and the other, which observes the northern, by Graham. Suspended to the western wall is the famous zenith sector, with which Bradley made the observations, at Kew and Wanstead, that led to the discoveries of the aberration of light, and the mutation of the earth's axis. The observations made at the Royal Observatory are universally allowed to possess an unrivalled degree of accuracy. M. Delambre, in a paper composed by him on the life and labours of Dr. Maskelyne, and read beforehe National Institute, Jan. 4, 1813, makes the following remark. "He (Dr. Maskelyne) has given a catalogue of stars, not numerous, but so accurate, as to have served, almost solely for the last 30 years, as the foundation of all astronomical researches. In short, it may be said of the four volumes of Observations which he has published, that if, by a great revolution, the sciences should be lost, and that this collection only were saved, there would be found in it sufficient materials to construct almost an entire edifice of modern astronomy; which cannot be said of any other collection." The following are the names of the astronomers who have officiated here in succession, with the times of their services respectively: Flamsteed, 43 years; Halley, 23 years; Bradley, 20 years; Bliss, 2 years; and Maskelyne, 46 years. Maskelyne has been succeeded by John Pond, Esq. F. R.S. who was appointed astronomer-royal in February 1812. Dr. Herschel's Observatory at Slough, near Windsor, though not a fixed one, will ever claim a distinguished place in the history of astronomical institutions. It differs from all other observatories in plan and apparatus; and it exceeds all others in the number of its discoveries. In describing this observatory, it should be premised, that Dr. Herschel's labours derive a peculiar character' and interest from the circumstance, that his discoveries are the result of his own inventions. For to his profound knowledge of astronomy he unites that of optics, both in theory and practice, by which he has been enabled to cast and polish mirrors for reflecting telescopes, greatly superior to any others, not only in magnifying power, but in South of the quadrant room is a small wooden building collecting, or, as it were, preserving light, by which vision for making occasional observations in any direction, where is wonderfully extended, and which he very expressively only the use of a telescope, and an accurate knowledge of denominates the power of penetrating into space." The the time, are required. It is furnished with sliding shut- telescopes, which are all made under his direction, are of ters on the roof and sides, to view any point of the hemi- various sizes, from two feet in length up to forty feet, and sphere, from the prime vertical down to the southern ho- the apparatus and machinery with which they are mounted rizon. It contains some excellent telescopes, particularly are also of his invention, and exhibit a very ingenious disa forty-inch achromatic, with a triple object-glass, and a play of mechanism. five-feet achromatic, both by Dollond; with a six-feet reflector, by Dr. Herschel. To the north of the observatory and east of the house are two small buildings, covered with hemispherical sliding domes, in each of which is an equatorial sector, by Sisson, and a clock, by Arnold. These are chiefly used for observing comets. Of the dwelling-house, the lower apartments are occupied by the astronomer-royal, and over them is a large octagonal room, which contains a great variety of astronomical instruments, with a library, consisting chiefly of scientific and scarce works. On the top of the house is an excellent camera obscura, which could not be better placed for the exhibition of interesting objects. In Flamsteed's time a well was sunk in the south-east corner of what is now the garden, behind the observatory, for the purpose of seeing the stars in the day-time, and observing the earth's annual parallax. It was a hundred feet deep, with stone stairs down to the bottom: but it has been long arched over, as the improvements in the telescope have rendered it unnecessary for astronomical purposes. As his larger telescopes could not be conveniently managed within the cover of a building, they are mounted in the open air, where they stand pointing to the heavens in different directions, and make a most magnificent and impressive appearance. Thus they are placed in what has been called the primitive observatory of man, "non sub tecto sed sub cœlo in puro dio." His largest telescope is 40 feet long and 5 in diameter. It contains a mirror of about a ton weight; and this great instrument, with nearly an additional ton of cases, &c, is managed by a very slight force. It is placed on a large circular frame, which turns on rollers, and the top is suspended by ropes from very lofty ladder-work. Thus, by a system of wheels, pinions, racks, and pulleys, the motions, both horizontal and vertical, are given, and hence any celestial object is readily found and commodiously viewed. It was finished in 1787, and on the first trial a new satellite of Saturn was discovered by it, and a second soon after. A very full and accurate account of his inventions and discoveries, as well as a particular description of his telescopes and their apparatus (with plates), will be found in the Philosophical Transactions, to which he has been a most importa contributor, having supplied that work with nearly 70 elaborate and ingenious communications. Two of his telescopes, of smaller size, are famous in the annals of discovery. The first is a two-feet Newtonian reflector, with which his sister Miss Carolina Herschel, whose astronomical attainments do great honour to her sex, discovered six comets; and the other is his seven-feet reflector, by which he discovered the Georgian planet at Bath, in 1781. This telescope has, in consequence of the discovery, been made a constellation in the heavens with the universal approbation of astronomers. It is placed between Gemini, the Lynx, and Auriga, and contains 81 stars. In Bode's atlas it is engraved with its apparatus, and marked Telescopium Herschelii. Dr. Herschel, though in his 76th year, is still an active and indefatigable observer. He was born at Hanover, Nov. 15, 1738, a period which will be ever memorable in the bistory of astronomy. The King's private Observatory in Richmond gardens is extremely beautiful in structure and apparatus, as well as in situation. It was built, in 1768, by order of his present majesty George 3, who, it is said, made several observations here, particularly of the transit of Venus in 1769. It contains a fine transit instrument, a zenith sector, and a mural arc, with several good telescopes, especially a ten-feet reflector of Dr. Herschel's. Here is a superb equatorial on the top of the building, which is covered with a moveable roof. There are also two fine orreries, with an excellent collection of philosophical instruments, and some cases of minerals and other natural curiosities. It was built under the direction of Dr. Demainbray, and has been, for some years, in the care of Mr. Rigaud. Oxford Observatory is a most magnificent structure, and the instruments perfectly correspond with the building. It was begun in 1772, from very ample funds bequeathed by Dr. Radcliffe, and the land on which it stands was the gift of the duke of Marlborough. The transit instrument, which is 10 feet long, shows very small stars in the day-time. It is said to have cost 150 guineas, the zenith sector 200 guineas, and the two mural quadrants 600 guineas. There are also very excellent telescopes and clocks here, the former by Herschel and Dollond, and the latter by Shelton. It was built under the direction of Dr. Hornsby, professor of astronomy in the university, who observed here for many years, and he has been succeeded by Dr. Robertson, the present worthy professor of astronomy. The observations are all registered, and consist chielly of the right ascensions and zenith distances of the sun, moon, planets, and fixed stars. In Dr. Hornsby's time, the registry was sometimes broken from ill health; for he had no assistant observer; but one has been of late added to the establishment, so that the observations will not, in future, be liable to the like interruptions. At Cambridge there have been small observatories at Christchurch, Trinity, St. John's, &c, and a plan is said to be now on foot for erecting one upon a great scale, and worthy the scientific fame of that learned university. Portsmouth Observatory.-At the Royal Marine Academy, Portsmouth, there is an observatory under the direction of Mr. Professor Inman, which is of peculiar utility, both in teaching the pupils practical astronomy, and in finding the rate of time-keepers for seamen. VOL. II. At Christ's Hospital, Mr. Wales (who had served under Dr. Maskelyne and Capt. Cook) erected a small observatory at his own expense, when he became master of the royal mathematical school there. The Royal Society have at Somerset House a small observatory, which is generally superintended by the secretary for the time being. At Highbury House, near Islington, an observatory was built in the year 1787, by Alexander Aubert, Esq, which, for perfection of plan and splendour of apparatus, perhaps has never been equalled by any private individual. This gentleman, whose scientific and liberal pursuits deserve honourable mention, died in the year 1806, and his grand collection of instruments was disposed of by auction, and of course dispersed. Similar notice may be taken of other observatories contemporary with that of Highbury, particularly those of Count Bruhl at Harefield, Sir George Shuckburgh at Shuckburgh, William Larkins, Esq. at Blackheath, and the Hon. Charles Greville at Milford, all of which were on a great scale, and have been discontinued after the demise of the owners. Thus in private observatories, though the astronomers may bequeath their apparatus to their heirs, they cannot transfer either their taste or their science. It is only in public establishments that permanence can be expected. Among the private observatories of the present day, the following alphabetical list may be also mentioned. Blackheath Blenheim Cambridge Chiselhurst Derby East Sheen Finsbury Square Godwood Gosport Hackney Wick Hayes Highbury Terrace Hoddesdon Islington Paragon, Southwark Park-lane Rose Hill, Sussex Sherburn St. Ibbs, Hitchin Woolwich' Stephen Groombridge, Esq. Duke of Marlborough. Rev. William Pearson. The Duke of Richmond. Earl of Macclesfield. Scotch Observatories.—In the different universities of Scotland professorships of astronomy have been established, but it has been here, as in most other universities, the theory of the science has been more attended to than the practice. At Edinburgh and Aberdeen there have been, however, observatories; and at Glasgow there is also a small one belonging to the college, but of late a magnificent one has been erected by a society of gentlemen, which is likely, when finished, to be very useful as well as honourable to that commercial city. Irish Observatories.-In Ireland two observatories have been established on a great scale, the one at Dublin, and the other at Armagh. The observatory 'belonging to Trinity-college, Dublin, commonly called the Dublin observatory, was begun in the year 1783. It was founded by Dr. Francis Andrews, provost of that college, who bequeathed a large income for this purpose. The apparatus are, a transit instrument of 6 feet focal length, with a 4 Irish Academy by mathematical and astronomical communications. feet axis, bearing 4 inches and a quarter aperture, with three different magnifying powers up to 600. An entire circle of 10 feet diameter on a horizontal axis for measuring meridian altitudes. An equatorial instrument, with circles of 5 feet in diameter: and an achromatic telescope, mounted on a polar axis, and carried by an heliostatic movement. Clocks were also ordered from Mr. Arnold, without any limitation of price. The situation chosen for the observatory is on elevated ground, about four English miles N. w. of Dublin. The foundation is a solid rock of limestone, of several miles extent; and the soil is very favourable, being a calcareous substance called limestone gravel, which is remarkable for absorbing the rain, and thus contributing to a dry atmosphere. The plan of the building unites at once both elegance and convenience. In the centre is a magnificent dome of three stories high, with a moveable roof for the equatorial instrument, which is placed on a pillar of 16 feet square, of the most substantial masonry, and surrounded by a circular wall at a foot distance, that supports the moveable dome, and also the floors, which in no part touch the pillar: thus, no motion of the floor or wall can be communicated to the instrument. The aperture for observation in the dome is two feet and a half wide. The most important erection belonging to this establishment is behind the main building, and at right angles to it, in order to obtain an uninterrupted view both north and south. This is the meridian or transit room, which contains both the transit instrument and the circle. It is 37 feet long, by 23 broad, and 21 high. Fine pillars of Portland stone are erected for both instruments on the most firm basis, and the floor is so framed as to let all the pillars rise totally detached from it. The clocks are attached to pillars of the greatest steadiness also: they were made by Arnold, who exerted his best skill, and are finished in a masterly manner; the pallets are of ruby; and all the last holes of the movement jewelled; the suspension springs are of gold, with Arnold's own fivebarred pendulum, and cheeks capable of experimental adjustment, so as to make all vibrations isochronal, whatever may be the excursion of the pendulum. The Rev. Dr. Usher, the first astronomy professor, did not long enjoy the pleasures of astronomy. He died in 1790, before the instruments had been all supplied. He was succeeded by the Rev. Dr. Brinkley, who was reared under Dr. Maskelyne, and had distinguished himself at Cambridge by profound analytical investigations, and who has since greatly enriched the Transactions of the Royal From a new 8 feet circle, by Berge, important results are expected, particularly on parallax, aberration of light, and refraction. Dr. B. has been for some time engaged in a series of observations with a view to explain the cause of variations which he has found in the zenith distances of certain stars at different times, which do not seem explicable by any cause at present generally allowed. He has found a difference between the zenith distances of a Lyræ, when in opposition and conjunction, which may be explained by a parallax of about 2 seconds. The new transit circle just erected at Greenwich possesses advantages for such purposes, and great hopes may therefore be formed from the concurrent operations of those two instruments. Armagh Observatory.-At Armagh, the metropolitan city of Ireland, and anciently the seat of a large university, an observatory has been erected and endowed in 1793, by the most reverend Richard lord Rokeby, then primate of Ireland. It is erected on the summit of a gently rising hill, about 90 feet above the general level of the town. The tower, which joins the dwelling-house, contains a very fine equatorial by Troughton, fixed on a large pillar, which is raised so high that the instrument in the dome can overlook all the buildings. To the cast of the house is a range of buildings for the transit room, and other astronomical purposes. The principal instruments, besides the equatorial and transit, are a ten-feet sextant by Troughton; a ten-feet reflecting telescope by Dr. Herschel; a five-feet triple object-glass achromatic telescope by Dollond; and also a fine night glass on an equatorial stand. The clocks are by Earnshaw of London, and Crossthwaite of Dublin. In this establishment a liberal income is allowed to the principal astronomer, and a good salary to his assistant. It has been superintended from the beginning by the Rev. James Archibald Hamilton, D. D. dean of the cathedral church of St. Coleman, Cloyne. The registered observations here, are those made with the transit instrument and equatorial; and also an account of the temperature and weight of the atmosphere. Of these, a series of about 18 years is preserved. The right ascensions of the sun and moon, compared with the fixed stars, are regular and unbroken; but their north polar distances have not been so constantly taken, as they are only observed by the principal astronomer, whose pastoral duties must occasionally interfere with his astronomical labours. ATABLE of the Longitudes and Latitudes of the principal Observatories of Europe, as deduced from the most recent and accurate Determinations. 55 45 45 2 30 48 8 20 0 46 OBSERVATORY Portable. See EQUATORIAL. OBTUSE Angle, one that is greater than a right-angle. OBTUSE-angled Triangle, is a triangle that has one of its angles obtuse: and it can have only one such. OBTUSE Cone, or OBTUSE-Angled Cone, one whose angle at the vertex, by a section through the axis, is ob tuse. OBTUSE Hyperbola, one whose asymptotes form an obtuse angle. OBTUSE-angular Section of a Cone, a name given to the hyperbola by the ancient geometricians, because they considered this section only in the obtuse cone. OCCIDENT, or OCCIDENTAL, west, or westward, in Astronomy; a planet is said to be occident, when it sets after the sun. OCCIDENT, in Geography, the westward quarter of the horizon, or that part of the horizon where the ecliptic, or the sun's place in it, descends into the lower hemisphere. OCCIDENT Equinoctial, that point of the horizon where the sun sets, when he crosses the equinoctial, or enters the sign Aries or Libra. OCCIDENT Estival, that point of the horizon where the sun sets at his entrance into the sign Cancer, or in our summer when the days are longest. OCCIDENT Hybernal, that point of the horizon where the sun sets at midwinter, when entering the sign Capri corn. OCCIDENTAL Horizon. See HORIZON. OCCULT, in Geometry, is used for a line that is scarce perceivable, drawn with the point of the compasses, or a black-lead pencil. Occult or dry lines are used in seve ral operations; as the raising of plans, designs of building, pieces of perspective, &c. They are to be effaced or rubbed out when the work is finished. OCCULTATION, the obscuration of any star or planet, by the interposition of the body of the moon, or any other planet. The occultation of a star by the moon, if 10 E observed in a place whose latitude and longitude are well determined, may be applied to the correction of the lunar tables; but if observed in a place whose latitude only is well known, it may be applied to the determining the longitude of the place. See CIRCLE. Circle of Perpetual OCCULTATION. OCEAN, the vast collection of salt water, which encompasses most parts of the earth. By computation it appears that the ocean takes up considerably more of what we know of the terrestrial globe, than the dry land does. This is perhaps easiest known, by taking a good map of the world, and with a pair of scissars clipping out all the water from the land, and weighing the two parts separately by which means it has been found, that the water occupies about two-thirds of the whole surface of the globe. The great and universal ocean is sometimes, by geographers, divided into three parts, As, 1st, the Atlantic and European ocean, lying between part of Europe, Africa, and America; 2d, the Indian ocean, lying between Africa, the East-Indian islands, and New Holland; 3d, the Pacific ocean, or great south sea, which lies between the Philippine islands, China, Japan, and New Holland on the west, and the coast of America on the east. The ocean also takes divers other names, according to the different countries it borders on as the British ocean, German ocean, &c. Also according to the position on the globe ; as the northern, southern, eastern, and western oceans. The ocean, penetrating the land at several straits, loses its name of ocean, and assumes that of sea or gulph; as the Mediterranean sea, the Persian gulph, &c. In very narrow places, it is called a strait, &c. OCTAEDRON, or OCTAHEDRON, one of the five regular bodies; contained under 8 equal and equilateral triangles.-It may be conceived as consisting of two quadrilateral pyramids joined together at their bases. To form an Octaedron. Join together 8 equal and equi |