On the time at which Nearchus left the Indus. 225 



fluid has even been put in a state of ebullition by the applica- 

 tion of red hot iron, and in a very few minutes has become 

 transparent, and the focus remained either exactly or very 

 nearly the same.* 



Art. V. — On the time at which Nearchus left the Indus. Com- 

 municated by the Author. 



Ihe connection of astronomy and chronology is a subject of 

 great interest as well as usefulness. It may not appear at first 

 sight to be a matter of much importance whether- an event 

 took place a few days sooner or a few days later ; but there is 

 great satisfaction, when, from the unerring aspect of the heaven- 

 ly bodies, we are able to fix the time at which any thing occur* 

 red. This gives a degree of precision as well as of authenticity 

 and certainty to an epoch which could hardly be derived from 

 any other source. With this view the following remarks were 

 drawn up. They do not lead us, indeed, to a variation from 

 a received interpretation, but they remove some difficulty which 

 may have remained on previous suggestions, and may add 

 something to that conclusiveness on which the mind loves to 

 rest. 



Dr Vincent's valuable work on the voyage of Nearchus may 

 not be in every one's hand ; it will be right, therefore, to quote 

 the words of it in making the statement of the present sub- 

 ject; and it will make the whole more easily understood by 

 general readers. He says*)-, " in regard to the second depar- 

 ture from the Indus, we have the united testimony of Strabo 

 and Arrian with a shade of difference, which, though it might 

 be well to reconcile, is not an object of importance. The date 

 of Arrian is the 20th of Boedromion, the date of Strabo is the 

 evening rising of the Pleiades, and both profess the authority of 

 Nearchus. 



" The evening rising of the Pleiades is fixed by Columella 



* Since this note was written Professor Barlow has found that the change 

 of position of the lens is .134 of an inch between 57° and each extreme, and 

 that the refractive index of the fluid is as its density. — Ed. 



f P. 34. 



