June 30, 1916] 



SCIENCE 



931 



merical terms of the original, some of which 

 can easily be misconstrued unless the form is 

 exactly noted. To reconcile if possible the 

 differences in the various manuscripts, and 

 then to identify the stars observed with the 

 present known positions, were the objects of 

 the revision. Any probable explanation of the 

 source of an error makes it easier to accept a 

 correction, and for such explanations a thor- 

 ough acquaintance with the language in 

 which the results were recorded, as well as 

 knowledge of the character of the results are 

 required. Both these requirements were ful- 

 filled in a remarkable degree by Dr. Peters. 

 Grounded in his astronomical training under 

 the tutelage of Encke and Gauss, he possessed 

 the painstaking and thorough habits of the 

 mathematical investigator, joined to a wide 

 culture from his varied life in different Euro- 

 pean countries. His residence of several 

 years at Constantinople gave him a fluent 

 knowledge of Turkish, Persian and Arabic, 

 besides his training in Greek, Latin and He- 

 brew, and his acquaintance with the usual 

 European languages, which the old time cul- 

 ture demanded of an educated man. Eollow- 

 ing his revolutionary experiences, he came to 

 this country in 1854, and soon after was 

 associated with Dr. B. A. Gould, in the Dudley 

 Observatory at Albany, which he left to be- 

 come professor of astronomy at Hamilton Col- 

 lege. In the period of over thirty years of his 

 directorship of the observatory at Clinton, he 

 made several trips abroad, and searched the 

 capitals of Europe for the manuscripts of the 

 " Almagest," sparing neither time nor labor 

 in studying every detail relating to the star 

 positions on record. The " Almagest " con- 

 tained a full summary of all existing knowl- 

 edge of the apparent movements of the sun, 

 moon and planets, the division of practical 

 astronomy to which the attention of the 

 earliest students of the sky would be most nat- 

 urally attracted. The seventh and eighth 

 books were devoted to the catalogue of north- 

 ern and southern stars, respectively. Ptolemy 

 did not accept any other explanation of the 

 universe than that of a central earth, without 



rotation, though ideas more in conformity 

 with the actual form of the solar system had 

 even at that time been more than once sub- 

 jects of speculation. The value of the ob- 

 liquity of the ecliptic was known, and the 

 effect of the precession could be closely calcu- 

 lated. His positions were given in longitude 

 and latitude, for an epoch known to be about 

 A.D. 138. But the earliest comparisons of his 

 positions showed that they were approximately 

 true for a much earlier period, following the 

 epoch of the observations of Hipparchus by 

 about one hundred and ninety years, thus cor- 

 responding nearly to the epoch a.d. 60. The 

 present publication, while presenting much of 

 the evidence from all points, adds nothing to 

 the solution of the question whether the places 

 of Ptolemy's catalogue were derived from any 

 observations of his own, or were simply the 

 observations of Hipparchus, brought up to the 

 later epoch by the addition of a constant cor- 

 rection to the longitudes, for the effect of pre- 

 cession. 



After Dr. Peters had begun his study of the 

 foreign manuscripts, Mr. E. B. Knobel, at one 

 time president of the Royal Astronomical So- 

 ciety, learned that they were both engaged 

 upon the same search; and as Dr. Peters did 

 not plan to work in the English museums and 

 libraries, they entered into hearty and unsel- 

 fish plans of collaboration, to include all avail- 

 able sources of authority. 



The description of their mutual labors has 

 been written by the English astronomer, and 

 the results have been tabulated by him, after 

 much extra discussion and transcription of 

 the original notes of Dr. Peters. In all, 

 thirty -two copies of the " Almagest," now pre- 

 served in Rome, Paris, Vienna, Venice, Oxford 

 and London, were examined by the two in- 

 vestigators, and the places of the stars from 

 twenty-six of these manuscripts have been 

 tabulated for comparison. The magnitudes 

 from seven manuscripts have also been tabu- 

 lated. The stars have been given Baily's num- 

 bers, consecutively, to No. 1,028, through the 

 various constellations in which the catalogue 

 of Ptolemy was collected. The places and 



