532 Astronomical Society. 



fraction being expressed by a dash annexed to the letter which in 

 common notation denotes the integer, frequent mistakes occur from 

 the copyist having affixed the dash when it ought not to be inserted, 

 and from omitting it when it ought to have been annexed. Thus 23° 

 is correctly denoted by ic y ; and 20° 20' (or 20°^) is correctly denoted 

 by K y' : again 34° is correctly denoted by X o ; and 30° 15' (or 30°|) 

 is correctly denoted by Xd'. Now it is very readily seen that mis- 

 takes of great moment may be made by the omission or misplacing 

 of the dash to the second letter : and here it is that the translation 

 from the Arabic frequently comes in to our aid ; for, as their notation 

 was not liable to the same sort of confusion, we are oftentimes 

 led to the true reading by a reference to their copies. I could point 

 out numerous instances of this kind ; one, however, will be quite 

 sufficient to illustrate my meaning. The star in Capricornus, the 

 fourteenth of that constellation in Ptolemy's catalogue, whose longi- 

 tude in all the above-mentioned editions, except the first, is said to 

 be 26°, is in the translation from the Arabic stated to be in longitude 

 20^°, or 20° 10' ; which is in fact its more correct value. Audit is 

 clear that the erroneous translation from the Greek has arisen from 

 not affixing the dash to the second letter in the expression k- s, which 

 ought to be K s'. Still there remain numerous other cases where this 

 mode of explication will not avail, and where it would be desirable 

 that other sources of information should, if possible, be thrown open 

 to us : and it is on this point, as I have before alluded, that I am 

 more especially induced to make the present appeal. 



Now, it appears that there are several works in this country that 

 might assist us very materially in the elucidation of this subject. 

 In the Bodleian library at Oxford there is a Greek manuscript of 

 . Ptolemy, which was presented by Selden ; and there is also, in the 

 same library, Bernard's copy of the Basil edition of 1538, wherein 

 he has copied out all the longitudes and latitudes of the stars in the 

 catalogue from this same manuscript. In the library of All Souls' 

 College, it is stated, by Fabricius, that there is the manuscript of a 

 Latin translation from the Arabic ; and I understand that there are 

 also manuscript Latin translations from the Arabic at New College 

 and at Magdalen College. There is also a manuscript commentary 

 in Persian, belonging to St. John's College. In the library of the 

 Archbishop of Canterbury at Lambeth there is also a Greek manu- 

 script of Ptolemy. In the library of the British Museum there is an 

 Arabic manuscript, of the date 1218 ; but I have not been able to 

 find there any Greek copy. 



It is evident, therefore, that we have in this country several sources 

 of original information, of which we might avail ourselves, to render 

 the catalogue of Ptolemy more perfect than it is ; and, lest it might 

 be supposed that this would be an useless labour at the present day, 

 when the state of the heavens is so much better known, I would re- 

 mark that it is on this very account that more accurate information 

 is required ; since we now know that many minute and gradual 

 changes are going on, which were not suspected or thought of in 

 former times, and which are only perceptible after a lapse of many 



