THE TIDES. 33 



and other extensive tracts of land, which consequently 

 give it a contrary dii-ectibn. 



In rivers the tides can flow only in a certain direc- 

 rion. Entering their mouths from the sea, and con- 

 fined within their banks, they must flow upward, and 

 sometimes meeting the current, especially in narrow 

 rivers, cause a great and rapid swell by forcing their 

 waters to flow backward. An example of the as- 

 tonishment which the observation of this natural phe- 

 nomenon formerly caused, and a proof of the impor- 

 tance of the study of nature, are afforded in a memo- 

 rable historical transaction. A fleet, equipped by 

 Alexander the Great, and commanded by his admiral, 

 Nearchus, having sailed down the Indus to the Per- 

 sian Gulph, the Grecian mariners, who had been un- 

 customed only to the navigation of the Mediterranean 

 and the .Egean Sea, or Archipelago, where tides are 

 unknown, were equally surprised and terrified on ob-* 

 serving the flax and reflux of the water at the mouth 

 of the Indus ; and regarded this phenomenon as an 

 unlucklv omen, and a decided mark of the displea- 

 sure of the gods against their expedition. Thus is it, 

 that ignorance is the parent of superstition, which 

 converts the ordinary appearances of nature into por- 

 tentous prodigies, and torments with groundless fears 

 the minds of those who are unacquainted with the Va- 

 rious operations of nature. 



With this important observation permit me to con- 

 clude this epistle, in order to prepare for the exhibi- 

 tion- of a novel scene : the display of animated na- 

 ture ; the contemplation of which will furnish you 

 with a copious fund of knowledge, and an ample 

 source of amusement. 



With every sentiment of affection and esteem, 

 I am, dear Sir, Your's, &c. 



c 5 



