512 TRANS. ST. LOUIS ACAD. SCIENCE. 



earlier eye-witnesses, must be respected so long as their traditions 

 are not clearly demonstrated to be impossibilities. This is and 

 will be the stand-point of all present and future historians, espe- 

 cially in reference to the chronology of the ecliptic new and full 

 moons witnessed by Greek and Roman authors. History is not 

 to be constructed a priori. 



S. The correctness of the Babylonian eclipses, as described in 

 Ptolemy's Almagest, is placed beyond question by careful calcu- 

 tions according to the most perfect Lunar Tables in existence, 

 viz. those of Hansen. This assertion, however, is likewise unten- 

 able. The Almagest specifies, as is known, in nearly all instances 

 in what hours and minutes each of its 19 eclipses commenced, in 

 what time they reached the middle, and came to a close ; more- 

 over, how many inches and minutes the moon's disc was obscured. 

 Supposing these minute measurements to have been the result 

 of Babylonian observations, those astronomers must, at least 

 since the year — 720, have been in the possession of instruments 

 capable of measuring the minutes of hours, and parts of inches 

 of the moon's diameter. In this case, of course, the specified 

 times and magnitudes of the Babylonian eclipses would agree 

 with each other. Now, if we compute the Babylonian eclipses by 

 means of the most accredited Lunar Tables — those of Hansen — 

 what is the result? One of them (No. 3) turns out to have been 

 invisible ; another one (No. 15) happened one hour and fifteen 

 minutes later than Ptolemy states ; another obscuration of the 

 moon (No. 6) amounted to one inch and fourteen minutes instead 

 of three inches, as the Almagest says. Let us come nearer to the 

 subject. Prof. Hartwich has taken upon himself to recalculate 

 Ptolemy's 19 eclipses by means of Hansen's Tables (Schumacher's 

 Astronom. Nachrichten, i860, No. 1241, p. 257), and the result 

 was that Ptolemy's statements differ very much from the compu- 

 tations. For, 



No. 2. Obscuration 0.206 (2J inches) instead of 0.250 (3 inches). 



No. 4. Obscuration 0,071 (J inch) instead of 0.250 (3 inches). 



No. 6. Obscuration 0.113 (^t inches) instead of 0.250 (3 inches). 



No. 7. Obscuration 0.022 (i inch) instead of 0.167 (2 inches). 



No. 14. Obscuration 0.671 (8J inches) instead of 0.583 (7 inches), etc. 



As to the times of Ptolemy's eclipses, the following incongrui- 

 ties came to light : 



