150 JDr Pearson, On a Manuscript Volume [Feb. 25^ 



(3) " On a Manuscript Volume of Astronomical Tables." 



Dr Pearson then exhibited another manuscript volume, 

 belonging to the same College, containing a number of Astro- 

 nomical Tables, and apparently dating from the seventeenth 

 century : as however it has been bound, since its completion, with 

 a number of blank leaves at either end; and as there is no name 

 or date whatever within the cover, we can only infer from the 

 fact that it appears in the large catalogue of MSS. of 1698 under 

 the same title, viz. Astronomicce Tabulce, as it now bears at the 

 back, that it is not u early so recent as that year. The suggestion 

 at first offered itself, that as Horrox was a member of the College, 

 and as it appears from Wallis's prefatory letter to his pub- 

 lished works \ that Jeremiah Shakerly, who afterwards obtained 

 possession of his papers, and who published Astronomical Tables 

 in 1653, followed up his studies on this subject, the volume might 

 be one of the sources from which he inferred the approaching 

 Transit of Venus of Nov. 24, 1639. It will be seen however on 

 examination, that Shakerly 's Tables could not well have been 

 borrowed from this MS. 



The Tables themselves are about xxxv. in number, though 

 they are not separately numbered as we find them in the volume: 

 they are very copious, each folio page containing about 60 lines of 

 figures, with about 30 entries (reckoning e.g. 5". 17'. 26" as three 

 entries) in each line: red ink is also used, as well as black, 

 wherever necessary : the whole volume consists of 298 foil, or 

 596 pp., accurately ruled, and perfectly legible and distinct 

 throughout. There is no index to the Tables ; but their contents 

 are always given at the top of the page. 



Table I. gives the mean motions (cequahiles motus) of the 

 precession of the equinoxes, and of the sun and their anomalies, for 

 each century commencing with the year B.C. 4000. The position 

 of the Sun at the equinox for that epoch, the whole Ecliptic being 

 divided into Sextants of 60", reckoned eastwards from the first point 

 of Aries, is given as v. 9". 23'. 20". 49'". 9"", for the year 400 B.C. 

 it is given as V. 59". 57'. 29". 44'". 7"", for the year 300 as — . 1". 

 21'. 13". 18'". 58"", which will assume the actual epoch when the 

 Sun was in that point at the vernal equinox to have been 370 B.C. 

 For the year 1800 the Sun's place at the Equinox is given as 

 — . 30". 39'. 28". 31'". 2""; fpr the year 1900, — . 32°. 3'. 12". 

 5'". 33"", from which data it can easily be seen how far the Table 

 is in error. 



Table II. gives the corresponding changes in the position of 

 the Moon's ascending node for the same period. 



Table III. gives similar computations for the Five greater 



Planets. 



1 Horrox, Opera Post. 1673. 



