iW PHILOSOPHICAL TRANSACTIONS. [aNNO 1751. 



gical, containing 5 tracts of different autliors concerning comets. One of them 

 intitled Tractatus fratris Egidii de cometis (written on account of a comet which 

 appeared in 1264) contains these passages relating to its place and motion. 



Prolog. " Stella caudata seu crinita apparuit in regno Franciac in oriente ante 

 solis ortum a 1 g" kalendas Augusti usque 5° nonas Octobris in anno Domini 

 1264. — Cap. 1. " Cometeni, cujus occasione haec scripsimus, primo vidimus 

 extra circulum zodiaci versus aquilonem contra cancrum, et demum eundem 

 vidimus extra circulum versus austrum sub geminis inter canem et orionem. — 

 Cap. 3. " Vidimus autem et stellam caudatam, cujus occasione hoc scripsimus, 

 praeter motum circularem diurnum, aeque moveri motu retrogradationis, et nulli 

 alii similis, secundum latitudinem ejus, quae est a septentrione ad austrum. 

 Visus est moveri per duos menses solares plusquam 40 gradus, vix per 3 gradus 

 longitudinis permutans situm. — Cap. 7- " Cometes, cujus occasione haec scrip- 

 simus, primo visa est in vespere post solis occasum, demum post paucos dies 

 solem pertransiens in mane circa octavum gradum cancri, et ex hinc cito pro- 

 cessit retro in geminos: vidimus autem et cometem moveri ab aquilone ad au- 

 strum, secundum latitudinem quidem plus 50 graduum, et secundum longitudem 

 quidem vix 5 gradus processisse." 



Hevelius in his Cometographia has also given the following paragraph, among 

 others, concerning this comet. " A. C. 1264, Stella, quae dicitur cometes, 

 apparuit, videlicet in oriente, ante ortum diei, post stellam matutinam ; apparuit, 

 scilicet, anteauroram cum radiis multis: ipsi ejus radii longe lateque apparuerunt 

 antequam oriretur ipsa Stella cometes. Igitur veloci cursu laboravit ipsa stella 

 cometes, ita quod prsecurrerit et longe versus meridiem praecessit stellam matu- 

 tinam, i. e. luciferum. Visa est circa festum S. Mariae Magdalenae, et usque ad 

 octavam S. Augustini apparuit. Compilat. Chronol." 



Though this whole account be very slender and rude, it is however much the 

 best Mr. D. had met with, of any comet earlier than that which was observed 

 by Regiomontanus in the year 1472, (except perhaps the account given byNice- 

 phoras Gregoras of the comet of the year 1337, whose orbit is computed by Dr. 

 Halley) ; for which reason, he was induced to try, whether he could investigate 

 a set of elements capable of representing the places of this comet agreeable to 

 the above description ; and after several attempts, some of them indeed but ten- 

 tative, he fixed on the following numbers for that purpose, viz. the place of its 

 ascending node in TI|^ 19°, the inclination of its orbit to the plane of the ecliptic 

 36j-°, the place of its perihelion in Vf 21°, its perihelion distance from the sun 

 44500 such parts as the mean distance of the earth from the sun contains 

 100000, and the time of its being in perihelion July 6^ 8^ p. m. The motion 

 of the comet in this orbit was direct. 



From these elements Mr. D. computed the places of the comet for the 



