228 On the time at which Nearchm left the Lulus. 



either on the very day the fleet sailed, or the next, or at the 

 latest, the next day but one.'" 



In a * postscript to his dissertation, (which is addressed to 

 Dr Vincent,) he mentions, that after he had finished his cal- 

 culations, he almost accidentally met with a passage in Usher, 

 in which the evening rising of the Pleiades is said to take place 

 on the 1st of October. He considers that Usher makes this 

 assertion on the authority of Euctemon, as cited by Geminus ; 

 and then adds with some exultation, " had you had the ill 

 luck to consult Usher's Ephemeris on Geminus, instead of 

 Columella, you would not have proposed this question to 

 Wales or me, for you would have taken it for granted that 

 Strabo and Arrian agreed. Had either he or I consulted them 

 before we calculated, we perhaps should not have engaged in 

 the labour of these calculations. We should have advised you 

 to follow Euctemon without regard to Columella, describing 

 the phenomena of another climate in another age ; but then we 

 should not have discovered what Wales has conjectured, and 

 my calculations, I think, put out of doubt ; that when the an- 

 cientsspeak of acronychal risings, they are to be understood of the 

 sensible acronysm ; and this is a principle which may prevent 

 many mistakes in deducing conclusions in chronology for these 

 astronomical characters of time which the ancients used. 1 ' 



It is not uncommon even for able men to be carried away 

 by the pleasure of a fancied discovery, and to make every 

 thing bend to the view which they have taken. This is the 

 case with Dr Horsley in the present instance ; and perhaps it 

 is not too much to say, that, if we wish for the exact truth, 

 we must seek for it in the contrary of almost every part of the 

 preceding passage. There is so much in Columella on the 

 times of the risings and settings of the stars, that we cannot 

 wonder at Dr Vincent's having recourse to him for his date. 

 He seems to have stated the question merely as a difficulty 

 which he had found in reconciling this authority with the 

 time mentioned by Arrian ; it is easy, therefore, to see the di- 

 rection which was given to Mr Wales's investigation. We 

 may trace the same effect, though more remotely, on Dr 

 Horsley ; for, although he particularly says,-)- " I have not 



• P. 521. | P. 505. 



