DISCOVERED FROM A STATEMENT OF DIODORUS S1CUI.US. 63 



a considerable distance of the moon's umbra, or that portion 

 of her shadow in which no part of the sun could be seen, or, 

 in other words, in which the eclipse would be total. 



The account given by Diodorus of the darkness in which 

 the fleet of Agathocles became enveloped, is confirmed by 

 Justin. It could scarcely be doubted, therefore, that the 

 eclipse was really a total one, at the place where it was 

 witnessed by the fleet. But in order that the phenomenon 

 should accord with the fact, as related by those historians, 

 the centre of the moon's shadow ought to be found to have 

 passed over, or very near to, the island of Malta : that is, the 

 latitude of the moon ought to be, at least, three minutes 

 greater than it was stated to be in the Astronomical Tables, 

 published by the French Board of Longitude, which Mr. 

 Baily employed in his computations. 



On account of this discordance, Mr. Baily expressed a 

 doubt of the accuracy of the amount of what is called the secu- 

 lar variation of the moon's mean distance from her node (on 

 which distance her latitude depends) as given in those tables, 

 although it had been deduced from the formulae of Laplace*. 



To question the accuracy of some of the most correct tables 

 of Astronomical quantities which had yet been produced, and 

 on a subject possibly involving the skill of the greatest Ma- 

 thematical Astronomer of modern times, on the authority of 

 a Greek historian, might have seemed a step very hazardous 

 to Mr. Baily's future reputation. The event, however, justified 

 this apparent presumption, confirming at once the authenticity 

 of the historian, and the accuracy of his astronomical commen- 

 tator. A few years after the publication of Mr. Baily's re- 

 searches, the French Board of Longitude printed a Supplement 

 to the Lunar Tables he had employed ; in which the quantities 

 termed the mean epoch and mean motion of the supplement 

 of the moon's node, were considerably altered, so as to bring 

 the latitude of the moon within the limits he had suggested t. 

 It was thus established by astronomical computation, in agree- 

 ment with historical authority, that the eclipse in question had 

 in reality been a total one, at the place where it had been seen 

 by the fleet of Agathocles. It is unnecessary to offer an ex- 

 tended comment upon this fact: nothing can show in a 

 stronger degree the value of ancient history to the cultivators 

 of science, nothing can better evince the utility of scientific 

 knowledge to the cultivators of Classical Literature. 



The same argument might be employed with respect to 



* Phil. Trans. 1811 ; or Phil. Mag. vol. xxxviii. p. 368. 

 f Phil. Mag. vol. Iv. p. 100, note. 



