VOL XLVII.] PHILOSOPHICAL TRANSACTIONS. 211 



months July, August, September, of the said year, which lie thinks agree as 

 well with the foregoing description as any regular computus can be expected to 

 do; and the resemblance of all the elements gives some ground for conjecture, 

 that this comet might possibly be the same with that which was observed by Paul 

 Fabritius and others in the year 1556, whose orbit Dr. Halley has computed. 

 (See his Synopsis Astronomiae Cometicae). Indeecl the change in the place of the 

 perihelion may perhaps be thought greater than could arise from the mutual gra- 

 vitations of the comets disturbing each other ; but then it may be considered, 

 that neither the place nor time of the perihelion, nor the perihelion distance of 

 the comet of the year 1556, could be determined very accurately from observa- 

 tions made only for 12 days, at 40 days distance from the perihelion, as those of 

 Fabritius were, unless they had been more exact than his appear to be. If these 

 were the same comet, its period is 292 years; and we may expect its return 

 about the year 1848. 



There are in the before-mentioned manuscript, besides the passages already 

 quoted from Egidius, two other places which deserve to be taken notice of. 

 One of them is so much of a small tract, intitled. Judicium de Stella Cometa, 

 Anno Domini 1301, as concerns the place and motion of the comet; it is as 

 follows: " A. D. Mccc primo, primo die Septembris apparuit cometa in occidente, 

 et per mensem vel amplius visus ftiit. — Ultima autem die Septembris duabus 

 horis 40 minutis post occasum solis — inveni quod longitudo cdmetae in signis et 

 gradibus erat 20 gradus scorpionis, et latitudo * 26 gradus septentrionalis : Mars 

 autem tunc erat in 20 gradu scorpionis directus exeuns, et sic fere conjuncti 

 erant Mars et cometa accipiendo loca ipsorum per circulum transeuntem per polos 

 zodiaci. — Verum et sexta die Octobris, scilicet in festo sanctse fidis post occasum 

 solis eadem hora inveni quod longitudo ejus erat primus gradus sagittarii, et lati- 

 tudo ejus 10 gradus septentrionalis. — Cometae latitudo ecliptica circa principium 

 apparitionis suae fuit 20 gradus et amplius septentrionalis, — Apparebat cometa 

 moveri a septentrione in meridiem per oriens, ita quod ejus longitudo orientalis 

 continue videbatur augeri, et ejus latitudo septentrionalis continue videbatur 

 diminui. — In principio apparitionis suae coma protendebatur ad septentrionem : 

 et post motum successive movebatur per orientem ad meridiem versus stellam 

 quae dicitur altayr hoc est vultur volans." 



Though this account is too imperfect for us to attempt determining the orbit 

 from, it may yet help us to know the same comet again, if any should hereafter 

 appear whose orbit will agree with this account ; which he believes none of those 

 already computed will do. 



• This figure (2) is a ditferent writing from the rest of the manuscript, and has manifestly been 

 altered since it was first \\riiten; it seems to have been 16" at the first, which I thmk the truerread- 

 ing.— Orjg. 



E £ 2 



