GEO 



the correftion of geography by the application of cclipfcG 

 of the fun and moon alone, as a fruitkfs and dcfperatc 

 undertaking. At length recourfe was had to the ech])fes of 

 the latelhtcs of Jupiler, and they were found effetlual for 

 the piirpofe. It was fome time, however, before the theory 

 Cif the fecondary phmets was regularly reduced to tables ; 

 and though Simon M.irius firil, and after him Baptitta Ho- 

 diema, compofed ephemerides of their motions, yet nothing 

 of that fort was found to be fufficicntly accurate for the pnr- 

 pofes of longitude, till M. Cafiirii publiflied his tables of the 

 revolutions and eclipfes of the fatellites in 1668. The firll 

 opportunity of eHcftually applying this theory to the 

 redifying of geography was fnggeited by M. Caffuii, and 

 taken by M. I'icard in 1671 and 1672, who, at the obferva- 

 tory of Tycho Rrahe at ITraniburgh, obferved two immcrfions 

 and three emerfions of the hrft fatellite of Jupiter, which 

 were afterwards compared witli the fame obferved by 

 M. CalTini at tlie obfervatory at Paris. This firll experi- 

 ment ^/X\e at once the difference of longitude in the clearelt 

 manner beyond the poiiibility of a doubt ; and it likewife 

 ;'.:Torded the certain profpecl of reftifying the whole extent 

 of geography as to longitude, upon principles that were felf- 

 cvident, and not liable to any miltake whatever. In confe- 

 quence of this fuccefs, M. Pieard and M. De la Hire, were 

 immediately employed in correcting the map of France ; in 

 •..onig wliich they v.ere obliged to contract it every where 

 withm lefs boundaries than it was fuppofed, according to 

 their former maps, to have occupied; infomucli that 

 Lewis XIV. jocofcly faid, that he found by their journey he 

 li.id fufPered a lofs of part of his kingdom. Other academi- 

 cians determined by the fame method the longitude of the ifle 

 ci Gorce, near cape Verd, on the coall of Africa, and of 

 ' luadaloupe and Martinico in the Weft Indies. And when 

 ■- Caffini had corrected his tables of the fatelhtes of Jupiter, 

 id pubh'hed a new edition of them in 1693, M. CiiazeUes 



• .ii lent up the Levant, to obferve the longitudes and 

 iitudes of Scanderoon, Alexandria, and Coaltantinople, 



• ■• order to determine the length and breadth of the Medi- 

 ,• iranean, which he executed with great abihty. 



Since the correction of longitudes has been introduced by 

 r.^'cnns of the fatellites of Jupiter, other methiids have been 

 ;ilfo adopted and devifed, which are proper and effectual for 

 lliat purpofe ; fuch as " the tranfits of Mercury and Venus" 

 over the body of the fun ; " occuitatioiis" of the fixed Itars 

 by the moon ; and flnce the lunar tables have been improved 

 t'V M. Mayer and others, another mode, equally applicable 

 1 this important objeft, has occurred, by meafuring from 

 time to time the exaft " distances of the moon from the 

 f-'.n," and "from a fixed itar" of the firll and fecond raag- 



• .'ude. In this mode there is a limitation of error, wliich 

 i ' far gives a degree of falisfaction, and prepares the way 

 f T brhiging the point that is thus unfettled to a more fpeedy 

 '; :d certain determination. Ini'lr'jments of obfervation have 

 iii!o been improved ; and time -pieces have been conitrufted, 

 i-eein a great degree from the error and uncertainty of thofe 

 tiiat were formerly in ufe. See Ciir.ONOMETEli and Clock. 

 oce alfo Epiie.meris and Longitude. 



For a fuller account of the hiitory of ancient geography 



f-e the preface to Bertius's edition of Ptolemy's Theatrum 



Gcographia; Vcteris, fol. For a brief hillory of the rife 



'id progrefs of geography, fee Varenius's Geog. and the 



' r.troduClion to Elair's Tables of Chronolog)'. 



The art, however, rauft needs have been exceedingly de- 

 ''5tive ; as a great part of the globe was then unknown : 

 J irticularly all America, the northern parts of Europe and 

 .'Vfia, with the Terra AullraliSj and Magellanica ; and as 



GEO 



they were ignorant of the eartii's being cajjr.ble of being 

 failed round, and of the toi-rid zones being habitable, &c. 



The principal writings on this art, among the ancients, 

 arc Ptolemy's eigjit books ; among the moderns are, Johannes 

 De Sacrobofco De Spha;ra, with Clavius's comment ; Ric- 

 cioliis's Geograj)hia and Hydrographia ReformaU ; 

 Weigelius's Speculum Terra: ; Dechales's Geography, in 

 his Mundus Mathcmaticus ; and above all, Varenins's Geo- 

 grapliia gencrahs, with Jurin's additions ; to which may be 

 added, Leibiiecht's Elementa Geographice generalis ; Stur- 

 mius's Compendium Geographicum ; Wolhus's Gcographia, 

 in his Elementa Miilhefeos ; the preface to M. Robert's 

 Atlas ; tiie introduction to Bufching's Geograpiiy ; the 

 works of Duval, Bnet, Deliile, D'Anviile,°Bonne, Bi- 

 rache, Mentelle, the Sanfons, Homann Morvilliers, Marti- 

 niere ; Pinkerton's Geography, Gordon's, Salmon's and 

 Gathrie's Grammars, &c. Hornii Orb. ant. delineatio, 

 Chiverius, Cellarius, Pomp. Mela, &c. &c. 



The reader will find under the appropriate terms in this 

 Cyclopedia, fuch information concernmg the fubjects wliich 

 they exprefs, as is confident with the nature and limits of 

 the work ; and it would be, therefore, ahogether fuper- 

 fluous to detail them in this place, and, in fo doing, to 

 tranfcribe articles that will be found in their proper places. 

 See Altitude, Amphiscii, Antipodes, Ant.?:ci, Cir- 

 cles, Climate, CoLuuEs, Degkee, Earth, Ecliptic, 

 Equator, Equinoctial, Globe, Heteroscii, Hokizon, 

 Latitude, Longitude, Map, Meuidian, Mountain, 

 OcKAN, Parallels, Peri.^ci, Periscii, Pole, Sphere, 

 Sphcft: Ojlique, Parallel, and Rig;it, Tropics, ZoNjei, 

 &c. &c. &c. 



GEOLOGY, in a Uriel fenfe of the word, or Geog- 

 nosy, is the fcience which illuitrates the ilructure, relative 

 pofition, and mode of formation of the diiFerent mineral fub- 

 llances that compofc the cruil of the earth. This interelUng 

 part of raineraiogy principally owes the dillinguilhed ranit 

 it now holds among the fciences to the celebrated protefibr 

 of Freyberg, who has however feparated geognofy, or the 

 fcience to which tlie above-given definition applies, from 

 geology in the fenfe in which the word is taken by him ; con- 

 fidering the latter as a merely fpeculative branch of know- 

 ledge, and as having nearly the fame relation to the former 

 which altrology has to allrcnomy. While geognofy, lefs in- 

 tent upon enquiring into the primordial ilate of the globe, 

 is contented v.-ith tlie merit of obferving, of collecting and 

 arranging fimple faCts in order to afcertain what cj.i be known 

 refpecling the relative fituation and agcsof mineral fubliances. 



Gcohgy (in the fenfe in which the word is taken by Wer- 

 ner) afpires to the higher merit of recording the events of 

 periods, when the planetary fyllem of v.-hich the earth forms 

 a part was yet uncreated, and of afligning caufes to effect<^, 

 and explaiwng phenomena, before it is afcertaincd whether 

 they really have exillence, or arc merely tlie offsprin'r of 

 fancy and ignorance. Tlie framers of moll of tho.'e tllTues 

 of extravagant notions, knoun by the appellation of iheorits 

 of the earth (fee Earth and Theories of the Earth,) haVi 

 been fatisfied v.-ith a very moderate fhare of ir.aterials for their 

 llruClures, not to mention th;:t moll of them were utterly- 

 unacquainted with the nature of the fubllances, the origin of 

 which they undertook to elucidate. Nothing is better cal- 

 culated to flatter felf-love than to be mentioned as the crea- 

 tor of a theory of the earth ; nothing eafier, with a moderate 

 (hare of imagination and hfs knowledge of facts, than to 

 frame a new theory fufficicntly dillinCt from all its } recurfors 

 to be noticed; and nothing fafer than to broach opinions 

 which, though they cannot be proved true by their authors, 



7 are 



