culated for fupporting the body in health, yet it INVESTIGATION OF THE CAUSES OF. As the can hardly be doubted but variety may be fafely love of life, and the defire of protracting ite indulged occafionally, if men would not exceed fhort fpan, are natural to all men, it feems to be the bounds of temperance. (See FOOD, § 4-6.) a public duty to examine minutely into the vari 3. and 4. Motion and reft, fleep and watching. It ous caufes that have been confidered as conducive is allowed on all hands, that alternate motion and to health and long life, and, if poffible, to diftinreft, and sleep and watching,are neceffary to health guifh fuch circumftances as are effential to that and longevity; and that they ought to be adapted great end, from thofe which are merely accidental. to age, temperament, conftitution, temperature But here it is much to be regretted, that an acof the climate, &c.; but the errors which man- curate hiftory of the lives of perfons remarkable kind daily commit in these refpects become a fruit- for longevity, fo far as relates to their diet, reful fource of difeafes. While fome are bloated gimen, &c. has not been faithfully handed down and relaxed with eafe and indolence, others are to us; without which it is impoflible to draw the emaciated, and become rigid by hard labour, neceffary inferences. It is indeed aftonishing, that watching, and fatigue. 5. Secretions and excretions. hiftorians and philofophers have hitherto paid fo Where the animal functions are duly performed, little attention to this important fubject. Were the fecretions go on regularly; and the different writers of abilities to undertake a full investiga evacuations fo exactly correfpond to the quantity tion of fo interefting a subject, the inquiry might of aliment taken in, in a given time, that the body prove not only curious, but highly ufeful. To is found to return daily to nearly the fame weight. furnish materials for a hiftory of longevity, the If any particular evacuation happen to be preter- bills of mortality throughout the kingdom ought naturally diminished, fome other evacuation is to be revised, and put on a better footing, agreeable proportionally augmented, and the equilibrium is to the fcheme of which Manchester and Chester commonly preferved; but continued irregularities, have already given a fpecimen worthy of imitation. in these important functions, cannot but terminate The plan might be further improved with very in difeafe. 6. Affections of the mind. The due re- little trouble, by adding a particular account of gulation of the paffions, perhaps, contributes the diet and regimen of every perfon who dies at more to health and longevity, than that of any 90 years of age or upwards; and mentioning wheother of the NON-NATURALS, as phyficians abfurd- ther bis parents were healthy, long-lived people, by ftyle them. The animating paffions, fuch as &c. An accurate regifter, thus eftablished throughjoy, hope, love, &c. when kept within proper out the British dominions, would be productive bounds, gently excite the nervous influence, pro- of many important advantages to fociety, not mote an equable circulation, and are highly con- only in a medical and philofophical, but alfo in ducive to health; while the depreffing affections, a moral and political view. fuch as fear, grief and despair, produce the contrary effect, and lay the foundation of the moft formidable difeafes. There is reafon to believe, that longevity is often in a great meafure heredi. tary, and that healthy long-lived parents would commonly tranfmit longevity and health to their children, did not the frequent errors in the nonnaturals daily fhorten human life. From thefe caufes, and the unnatural modes of living, nearly one half of all the children born in the capital cities of Europe die in infancy. Such an amazing proportion of premature deaths is not to be found among favage nations, or among the young of other animals! Man feems naturally defined to rife with the fun, to spend a large portion of his time in the open air, to inure his body to robuft exercises and the inclemency of the feafons, and to make a plain repatt when hunger dictates. Such was the patriarchal life. But art and inxury have defeated the plan of nature; and, by enhaving him to all the blandithments of fenfe, has, rendered him an eafy victim to vice and difeafe. To enumerate the various abufes which take place from infancy, and are continued through every ftage of modifh life, would lead us far beyond our prefent fubject. Suffice it to obferve, that they prevail most among people who are the most highly polished and refined. To compare their artificial mode of life with that of nature, or even with the long-livers in the above lift, (§ 3.) might afford a very ftriking contraft; and at the fame time fupply an additional reaton, why in large cities, inftances of longevity are so very rare. (6) LONGEVITY, PROPOSAL FOR AN ACCURATE (1.) LONGFORD, a county of Ireland, in the province of Leinfter, bounded by the counties of Leitrim and Cavan on the N. Meath on the E. and S. and Rofcommon on the W. It contains 134,700 Irish plantation acres, 24 parishes, 6 baronies, and 4 boroughs; and before the Union, returned 10 members to parliament. It now fends 2 reprefentatives to the Imperial parliament. It has a tolerable good foil, but much encumbered with marshes; and is about 25 miles long, and 16 broad. (2.) LONGFORD, the capital of the above county, is fituated on the Cromlin, which falls, a few miles below, into the Shannon. It is a borough and market town, and has a barrack for a troop of horfe. It is large and well built; and in a very enly age an abbey was founded here, of which St Idos, one of St Patrick's difciples, was abbot. In 1400, a fine monaftery was founded for Dominican friars, by O'Ferral, prince of Annaly. Being deftroyed by fire, Pope Martin V. in 1429, and Eugene IV. in 1433 and 1438, granted indulgences to all who should contribute to the rebuilding of it. The church of this friary, now the parith church, is in the diocefe of Ardagh. There are 4 fairs. Longford is 64 miles NW. by W. of Dublin. Lon. 8. o. W. Lat 53. 42. N. (3-7.) LONGFORD is alfo the name of 5 Englith villages; in Derby, Gloucester, Middlesex, Salop, and Wilts. (1.) LONGFORGAN, a parifh of Scotland, in the SE. corner of Perthshire, 7 miles long, and nowhere above 34 broad, but in fome places very narrow; containing about 7000 acres, all in high cultivation, bounded for 3 miles on the S. by the Ddd 2 Tax Tay. The climate is mild and falubrious; the furface partly hilly; the foil fertile, and much improved by levelling, embanking, draining, &c. producing excellent crops of wheat, barley, oats, peafe, potatoes, yams, lintfeed, turnips, clover, hay, &c. There are five orchards abounding in fruits, befides fine gardens at Castle Huntly, which produce peaches, nectarines, apricots, almonds, figs, melons, &c. Thefe have above 300 feet of glafs, and a melon-pit, 20 feet by 12, fo conftruct. ed as to receive the fteam from a boiler of caft iron, containing 10 gallons, built in a chamber that occupies the whole fpace under the melon bed. The melons thus produced are highly flavoured. The population, in 1797, was 1526; increafe 241 fince 1755: number of horfes, 347; sheep above 400; and black cattle 900; befides calves, pigs, poultry, 8 dove-cots, and great numbers of hares, foxes, partridges, &c, Bee hufbandry is much cultivated, and excellent honey produced. Servitudes are abolished, and the roads are good. Caftle Huntly is the moft ancient and remarkable edifice, being feated on the point of a fingular rock, in the middle of a plain, 116 feet perpendicular in height on the SW. and floping gradually to the E. The profpect from its top is one of the grandeft in Perthshire; commanding a view of the Tay for 20 miles, and of Fife and Angus fhires for above 60. The parish abounds with wood, fhell marl, and excellent ftone quarries. (2.) LONGFORGAN, a village in the above parith, occupying 23 Scots acres, on the E. corner of the Carfe of Gowrie. It was erected into a burgh of barony in 1672, by Charles II. with a market and a fairs, on 3d Wed. of June and Oct. It contained 126 families and 630 fouls, in 1796. It lies 12 miles ENE. of Perth. Lon. 3° 16 45" W. Lat. 56° 27′ 48′′ N. LONGFORMACUS, a hilly parish of Scotland, in Berwickshire, 11 miles long, and 6 broad. The furface is moftly covered with heath. Oats, barley, peafe, clover, and rye-grafs, are raised on a few acres improved by lime. The air is dry, cold, and piercing. The population, in 1790, was 452, increafe 53 fince 1755 number of horses 70; black cattle 200; and sheep 10,000, Some cart loads of rich copper ore have been dug up in making a road, but the mine is not wrought. LONGHAVEN, a bay on the W. coaft of Aberdeenshire, 4 miles S. of Peterhead. * LONGIMANOUS. adj. [longuemain, French; longimanus, Lat.] Longhanded; having long hands. The villainy of this Chriftian exceeded the perfecution of heathens, whofe malice was never fo longimanous as to reach the foul of their enemies, or to extend unto the exile of their elysiums. Brown's Vulgar Errours. (1.)* LONGIMETRY. n. f. longus and urgi; Jongimetrie, French.] The art or practice of meafuring distances.-Our two eyes are like two different ftations in longimetry, by the affiftance of which the distance between two objects is meafured. Cheyne's Phil. Principles. (2.) LONGIMETRY is properly the art of mea furing lengths, both acceffible and inacceffible. See GEOMETRY and TRIGONOMETRY. (1.) * LONGING. n. f. [from long.] Earnest defire; continual wish.-When within short time I came to the degree of uncertain wishes, and that thofe wishes grew to unquiet longings, when I would fix my thoughts upon nothing, but that within little varying they should end with Philo clea, Sidney.I have a woman's longing, An appetite that I am fick withal, To fee great Hector in the weeds of peace. Shak, The will is left to the purfuit of nearer fatisfactions, and to the removal of those uneafinesses which it then feels in its want of, and longings after them. Locke. (2.) LONGING is a preternatural appetite in pregnant women, and in fome fick perfons when about to recover. It is called PICA, from the bird of that name, which is faid to be fubject to the fame diforder. It confifts of a defire of unufual things to eat and drink, and in being foon tired of one and wanting another. It is called MALA CIA, from aan, weakness. Chlorotic girls, and men who labour under fuppreffed hemor rhoids, are very fubject to this complaint, and are relieved by promoting the refpective evacua. tions. In general, whether this diforder is obferved in pregnant women, in perfons recovering from an acute fever, or in those who labour under obftructions of the natural evacuations, this craving of the appetite should be indulged. * LONGINGLY. adv. [from longing.] With inceffant wishes. To his firft bias longingly he leans. Dryden, LONGINICO, the ancient OLYMPIA, Ste LANGANICO and OLYMPIA. (1.) LONGINUS, Dionyfius, a celebrated Greek critic of the 3d century, by fome faid to have been born in Athens, by others in Syria. His father's name is unknown, but by his mother he was allied to the celebrated Plutarch. His youth was spent in travelling with his parents, which gave him an opportunity to increase his knowledge, and improve his mind. After his travels, he fixed his refidence at Athens, and with the greateft affiduity applied to study. Here he published his Treatife on the Sublime; which raised his reputation to fuch a height, and gave the Athenians fuch an opinion of his, judgment and tafte, that they made him fovereign judge of all authors, and every thing was received or rejected by the public, according to his decifions. He feems to have staid at Athens a long time; here he taught the academic philofophy, and among others had the famous Porphyry for his pupil. But it was at length his fortune to be drawn from Athens, and to mix in more active fcenes; to train up young princes to virtue and glory; to guide the bufy paffions of the great to noble ob jects; to ftruggle for, and at laft to die, in the caufe of liberty. ZENOBIA, queen of the Eaft, prevailed on him to undertake the education of her fons; and he foon gained an uncommon fhare in her efteem: she spent the vacant hours of her life in his conversation, and modelled her fentiments and conduct by his inftructions. That princefs was at war with Aurelian: and being defeated by him near Antioch, was compelled to shut herself up in Palmyra, her capital city. The emperor wrote her a letter, in which he ordered her to partment of the Rubicon, and late province of Romagna. to furrender; to which the returned an answer, drawn up by Longinus, which filled him with refentment. The emperor laid fiege to the city; and the Palmyrians were at length obliged to furrender. The queen and Longinus endeavoured to fly into Perfia; but were overtaken and made priToners, when on the point of croffing the Euphrates. The queen, intimidated, weakly laid the blame of vindicating the liberty of her country on its true author; and the brave Longinus, to the difgrace of the conqueror, was immediately executed. (See PALMYRA.) The writings of Longinus were numerous, fome on philofophical, but the greater part on critical fubjects. Dr Pearce has collected the titles of 25 treatifes, none of which, excepting that on the Sublime, have efcaped the depredations of time and barbarians. On this imperfect piece the great fame of Longinus is raifed, who, as Pope expreffes it, "is himself the great fublime he draws." The beft edition of his works is that of Tollius, printed at Utrecht in 1694, cum notis variorum. It has been tranflated into English by Mr Smith. (2.) LONGINUS. See ITALY, 14; and LoмBARDS, 3. LONGIONO, a town of Italy, in the de L DEFINITIONS. *LONGISH. adj. [from long.] Somewhat long, LONG ISLAND, an island of New York, feparated from the continent by a narrow channel. It extends from the city of New York 140 miles E. terminating with Montauk point; and is 10 miles broad. It is divided into 3 counties, King's, Queen's, and Suffolk. The S. fide is flat land, of a light fandy foil, bordered on the fea-coaft with large tracts of falt marsh and meadow, extending from the W. point of the island to Southampton; and well calculated for raifing Indian corn. The N. fide is hilly, and of a ftrong foil, adapted to grain, hay, and fruit. A ridge of hills extends from Jamaica to South-hold. Large herds of cattle feed upon Hampstead plain, in Queen's county, which is 16 miles long, from E. to W. and 7 or 8 broad. It is frequented by vast numbers of plover. Rye grows tolerably well, but moft part of the plain lies common for cattle, horfes, and sheep. The island contained 32,TIO citizens, and 4839 flaves, in 1795 LONGISSIMUS DORSI, See ANATOMY, § 209, 15. LONGITUDE.. ONGITUDE is thus defined and illuftrated by Dr Johnson: * LONGITUDE. . f. [longitude, French; longitudo, Latin.] 1. Length; the greatest dimenfion. The ancients did determine the longitude of all rooms, which were longer than broad, by the double of their latitude. Wotton.-The variety of the alphabet was in mere longitude only; but the thousand parts of our bodies may be diverfified by fituation in all the dimenfions of folid bodies;. which multiplies all over and over again, and overwhelms the fancy in a new abyfs of unfathomable number. Bentley. This univerfal gravitation is an inceffant and uniform action by certain and eftablished laws, according to quantity of matter and longitude of diftance, that it cannot be de, ftroyed nor impaired. Bentley. 2. The circumference of the earth measured from any meri. dian.-Some of Magellanus's company were the firft that did compass the world through all the degrees of longitude. Abbot. 3. The diftance of any part of the earth to the east or weft of any place. To conclude: Of longitudes, what other way have we, But to mark when and where the dark eclipfes be? Donne. -His was the method of discovering the longitude by bomb veffels, Arbuth. and Pope's Mart. Scrib. 4. The pofition of any thing to eat or weft.-The longitude of a ftar is its diftance from the first point of numeration towards the east, which firft point, unto the ancients, was the vernal equinox. Brown. LONGITUDE, in geography and navigation, is the distance of any place from another eastward or weftward, counted in degrees upon the equator; but when the distance, is reckoned by leagues or miles, and not in degrees, or in degrees on the meridian, and not of the parallel of latitude, in which cafe it includes both latitude and longitude, it is called departure. Although the LONGITUDE, properly speaking, can neither be ftyled a feience, nor even a branch of a science, yet the methods and inftruments invented to difcover it at fea, form fo important a branch of the sciences of navigation and geogra phy, that we think it proper to infert every thing refpecting it, in the ufual form of the fciences in this work. We fhall therefore give, 1. A brief hiftory of the attempts made to discover it: 2, An account of fome defiderata ftill required to complete the difcovery: 3. Practical directions for finding it: And, 4. Examples of the methods generally used for that purpofe. SECT. I. HISTORY of the ATTEMPTS made to difcover the LONGITUDE at SEA. To find the longitude at fea, is a problem to which the attention of navigators and mathema. ticians has been drawn ever fince navigation be, gan to be improved. The importance of this problem foon became fo well known, that, in 1598, Philip III. of Spain offered a reward of 1000 crowns for the folution; and his example was foon followed by the States General, who offered 10,000 florins. In 1914, an act was paffed in the British parliament, empowering certain commiffioners to make out a bill for a fum not exceeding 2000l. for defraying the neceffary expenses of experiments for afcertaining this point; and likewife granting a reward to the perfon who made any progrefs in the folution, proportionable to the degree of accuracy with which the folution was was performed: 10,000l. was to be granted if the longitude should be determined to one degree of a great circle, or 60 geographical miles; 15,000l. if to two thirds of that diftance; and 20,000l. if to the half of the diftance. In confequence of thefe offered rewards, innumerable attempts were made to discover this important fecret. The firft was that of JOHN MoRIN, profeffor of mathematics at Paris, who propofed it to Cardinal Richelieu; and though it was judged infufficient on account of the imperfection of the lunar tables, a penfion of 2000 livres per annum was procured for him in 1645 by Cardinal Mazarine. Gemma Frifius had indeed, in 1530, projected a method of finding the longitude by means of watches, which at that time were newly invented; but the ftructure of these machines was then by far too imperfect to admit of any attempt; nor even in 1631, when METIUS made an attempt to this purpofe, were they advanced in any confiderable degree. About 1664, Dr.Hooks and Mr HUYGENS made a very great improvement in watchmaking, by the application of the pendulum fpring. Dr Heoke having quarrelled with the miniftry, no experiment was made with any of his machines; but many were made with thofe of Mr Huygens. One experiment, particularly, made by Major HOLMES, in a voyage from the coaft of Guinea in 1665, answered fo well, that Mr Huygens was encouraged to improve the ftructure of his watches; but it was found that the variations of heat and cold produced fuch alterations in the rate of going of the watch, that unless this could be remedied, the watches could be of little ufe in determining the longitude. A whimfical method of finding the longitude was propofed by Meffrs WHISTON and DITTON, from the report and flafh of great guns. The motion of found is known to be nearly equable, from whatever body it proceeds, or whatever be the medium. Suppofing therefore a mortar to be fired at any place, the longitude of which is,known, the difference between the moment that the flash is feen and the report heard will give the diftance between the two places; whence, if we know the latitudes of these places, their longitudes muft alfo be known. If the exact time of the explosion be known at the place where it happens, the difference of time at the place where it is heard will likewife give the difference of longitude. Let us next suppose the mortar to be loaded with an iron fhell filled with combuftible matter, and fired perpendiculary upward into the air, the fhell will be carried to the height of a mile, and will be feen at the distance of near 100; whence, fuppofing neither the flash of the mortar fhould be feen nor the report heard, ftill the longitude might be determined by the altitude of the hell above the horizon. According to this plan, mortars were to be fired at certain times, and at proper ftations, along all frequented coafts, for the direction of mariners. This indeed might be of ufe, and in ftormy wea ther might be a kind of improvement in lighthouses, or a proper addition to them; but with regard to the determination of longitudes is evidently ridiculous, In 1714, HENRY SULLY, an Englishman, printed a fmall tract at Vienna, upon the fubject of watch-making. Having afterwards removed to Paris, he applied himself to the improvement of time-keepers for the discovery of the longitude. He taught the famous JULIAN DE ROY; and this gentleman, with his fon, and M. BERTHOUD, are the only perfons, who, fince the days of Sully, have turned their thoughts this way. But though experiments were made at fea with fome of their watches, they were not able to accomplish any thing of importance with regard to the principal point. The firft who fucceeded in any confiderable degree was Mr JOHN HARRISON; who, in 1726, produced a watch which went fo exactly, that for ten years together it did not err above ne fecond in a month. In 1736 it was tried in a voyage to Lifbon and back again, on board one of his Majefty's fhips; during which it corrected an error of a degree and an half in the computation of the fhip's reckoning. In confequence of this he received public encouragement to go on; and by the year 1761, had finished three timekeepers, each of them more accurate than the former. See HARRISON, N° 2. The laft turned out fo much to his fatisfaction, that he now applied to the commiffioners of longitude for leave to make an experiment with his watch in a voyage to the Weft Indies. Permiffion being granted, his fon Mr William Harrifon fet out in his Majefty's fhip the Deptford for Jamaica in the month of November 1761. This trial was attended with all imaginable fuccefs. The longitude of the island, as determined by the time-keeper, differed from that found by astronomical obfervations only one minute and a quarter of the equator; the longitude of places feen by the way being alfo determined with great exacnefs. On the fhip's return to England, it was found to have erred no more during the whole voyage than 1′ 54′′ in time, little more than 18 miles in diftance; which being within the limits prefcribed by the act, the inventor claimed the L. 20,000 offered by government. Objections, however, were started. Doubts were pretended about the real longitude of Jamaica, as well as the manner in which the time had been found both there and at Portsmouth. It was alleged alfo, that although the time-keeper happened to be right at Jamaica, and after its return to England, this was by no means a proof that it had always been fo in the intermediate times; in confequence of which allegations, another trial was appointed in a voyage to Barbadoes. Precautions were now taken to obviate as many of thefe objections as poffible. The commiffioners fent out proper perfons to make aftronomical obfervations at that ifland; which, when compared with others in England, would afcertain beyond a doubt its true fituation. In 1764, then, Mr Harrison junior fet fail for Barbadoes; and the result of the experiment was, that the difference of longitude betwixt Portsmouth and Barbadoes was thown by the time-keeper to be 3 h. 55' 3"; and by aftronomical obfervations to be 3 h. 54' 20" the error being now only 43" of time, or 10' 45" of longitude. In confequence of this and the for mer mer trials, Mr Harrison received one half of the reward promised, upon making a difcovery of the principles upon which his time-keepers were conftructed. He was likewife promised the other half of the reward as foon as time-keepers fhould be conftructed by other artists, which fhould anfwer the purpose as well as thofe of Mr Harrifon him felf. At this time he delivered up all his timekeepers, the laft of which was fent to Greenwich to be tried by Mr Nevil Maskelyne the aftronomer royal. On trial, however, it was found to go with much lefs regularity than had been expected; but Mr Harrison attributed this to his having made fome experiments with it which he had not time to finish when he was ordered to deliver up the watch. Soon after this an agreement was made by the commiffioners with Mr Kendall to conftruct a watch upon Mr Harrison's principles; and this upon trial was found to answer the purpose even better than any that Harrison himself had conftructed. This watch was fent out with Capt. Cook in 1772; and during all the time of - his voyage round the world in 1772, 1773, 1774, and 1775, never erred quite 14 feconds per day: in confequence of which, the house of commons, in 1774, ordered the other L. 10,000 to be paid to Mr Harrison. Still greater accuracy, however, has fince been attained. A watch was lately conftructed by Mr ARNOLD, which, during a trial of 13 months, from Feb. 1779 to Feb. 1780, varied no more than 6'69" during any two days; and the greateft difference between its rates of going on any day and the next to it was 4'11". The greatest error it would have committed therefore in the longitude during any fingle day would have been very little more than one minute of longitude; and thus might the longitude be determined with as great exactnefs as the latitude generally can.-This watch, however, has not yet been tried at fea. SECT. II. OF CERTAIN DESIDERATA fill requifite to PERFECT the DISCOVERY of the LONGITUDE. THE method of constructing time-keepers for discovering the longitude feems to be brought to as great a degree of perfection as can be expected. Still, however, as thefe watches are fubject to accidents, and may thus alter the rate of their going without a poffibility of a discovery, it is neceffary that fome other method fhould be fallen upon, to correct from time to time thofe errors which may arife either from the natural going of the watch, or from any accident which may happen to it. Methods of this kind are all founded upon celestial observations of some kind or other; and for these methods, or even for an improvement in time-keepers, rewards are ftill held out by government. After the discoveries made by Mr Harrison, the act concerning the longitude was repealed, excepting fo much of it as related to the conftructing, printing, publishing, &c. of nautical almanacks and other useful tables. It was enacted also, that any person who fhall discover a method for find ing the longitude by means of a time-keeper, the, principles of which have not hitherto been made public, shall be entitled to a reward of L.5000, if, after certain trials made by the commiffioners, the faid method fhall enable a fhip to keep her longitude during a voyage of fix months within 60 geographical miles or a degree of a great circle If the fhip keeps her longitude within 40 geographical miles for that time, the inventor is entitled to a reward of L.7500, and to L.10,000 if the longitude is kept within half a degree. If the method is by improved aftronomical tables, the author is entitled to L.5000 when they show the dif tance of the moon from the fun and ftars within 15 feconds of a degree, anfwering to about 7 minutes of longitude, after allowing half a degree for errors of observation, and under certain reftrictions, and after comparison with aftronomical obfervations for a period of 184 years, during which the lunar irregularities are fuppofed to be completed. The fame rewards are offered to the per fon who fhall, with the like accuracy, discover any other method of finding the longitude. These methods require celeftial observations; PRACTICAL DIRECTIONS for FIND- We now proceed to give fome practical directions for finding the longitude at fea by proper celeftial obfervations; exclufive of those from Jupiter's fatellites, which, for reasons just mentioned, cannot be practifed at fea. In the firft place, however, it will be neceflary to point out fome of thofe difficulties which ftand in the way, and which render even this method of finding the longitude precarious and uncertain. Thefe lie principally in the reduction of the obfervations of the heavenly bodies made on the surface of the earth. to fimilar obfervations fupposed to be made at the centre; which is the only place where the celeftial bodies appear in their proper fituation. It is alfo very difficult to make proper allowances for the refraction of the atmosphere, by which; all objects appear higher than they really are; and another difficulty arifes from their parallaxes, which |