VOL. XIH.] PHILOSOPHICAL TBAN8ACTI0NS. 55g 



gibbous figure; except that on Sept. 8 especially, a very bright ray proceeded 

 from the nucleus, which was rather crooked, and passed into the tail. This is 

 the more remarkable, as I do not remember to have seen the like appearance in 

 any other comet. It may also be observed, that sometimes its tail was directed 

 pretty exactly in opposition to the sun, as Aug. 30 in the morning; but often 

 with a considerable deviation, as is usual in most comets. Its coma was also of 

 various lengths: for, at first the tail was of about J 2° long; afterwards rather 

 shorter, and sometimes longer, as far as to 15° or 1 6°; but towards the end it 

 diminished continually. See %. 2, pi. l6. 



An Account of some Books. N** 143, p. 20, 



I. KAauJ'jou Tlro'Kifjt.a.iox) AfjiAonxwi/ BiSxia y. Claudii Ptolemaei* Harmonicorum 

 Libri Tres. Ex Codd. Mss. Undecim, nunc primum Graece editi. Johannes 

 Wallis, ss. Th. D. Geometriae Professor Savilianus Oxoniae, Regiae Societatis 

 Londini Sodalis, Regiaeque Majestati a Sacris; recensuit, edidit, Versione et 

 Notis illustravit, et Auctarium adjecit. Oxonii^ e Theatro Sheldoniano, A. D. 

 l682. In Quarto. 



This work having been never before printed in Greek, and but very imper- 

 fectly in Latin, by Anton. Gogavinus of Graves, above 100 years since: the 

 learned professor thought fit to give it in a more perfect edition. For which 

 purpose he has diligently compared the manuscript copies, for restoring and per- 

 fecting the Greek text ; and adjoined a new Latin translation of the whole, with 

 notes on the text : rectifying many mistakes of the transcribers, especially in the 

 numbers. 



This work of Ptolemy gives an account of the nature of sounds in general, 

 but especially of those that are musical; as, of the several sorts of tones, and 

 their ratios one to another, &c. Showing also how harmony may be fitly com- 

 pared to the motions of the human soul ; and those of celestial bodies. And it is 

 the more considerable, as being not only the best of the kind in Greek, but as 

 it also gives an account of the rest; wherein they agreed or disagreed, one with 

 another, and on what principles. 



* Claudius Ptolemy, or Ptolomy, was a celebrated mathematician of Pelusium, who flourished 

 under Adrian, and Marcus Aurelius, about the year 138, and who left several other valuable works, 

 besides that above noticed. As, 1, his geography, first printed at Bologna, 1462, in folio, and several 

 times since, 2. Some astronomical works, the principal among them the Almagest, first printed at 

 Basil, 1351, folio. 3. Some works on judicial astrolog}', &c. in 1535. He is also celebrated on 

 account of the system of the universe, called by his name, in which the earth is placed in the centre 

 of the planetary system] a system which was adopted by astronomers for many ages, but is now 

 totally abandoned for that of Copernicus. 



