266 



TIDES IN THE 



In September, the freshes are at their height, there is no visible tide 

 off Calcutta, the ships do not swing up, and the river water is perfectly 

 sweet, far beyond Saugor in the open sea. The high parallax of the 

 moon at the equinoxes, with the great height of the sea, produces a heavy 

 bore in this month. 



The Bores. 



The bores in the Hoogly occur only on the highest, or at alternate 

 spring tides ; their appearance maj?-, with certainty, be predicted by the 

 season of the year, and the parallax of the moon. During the months of 

 November, December, January, and February, or on the periodical ebb 

 of the sea, when the currents are setting down the Bay, the tides, as may 

 be supposed, are languid, and consequently, during this period, there are 

 no bores.* 



As soon as the south-west monsoon sets the currents up the Bay, 

 the sea begins to rise, the tides become strong and high, and bores follow 

 in their train ; whenever the parallax of the moon is high on the springs 

 during the south-west monsoon, bores will certainly make their appear- 

 ance, and when strong southerly winds are added, and freshes withheld, 

 the height of the bores will be increased. 



It 



* Except very rarely — In twenty-two years I liave known but three instances. Agreeably to the 

 Statement of local causes which accelerate or depress the tides, it will be obvious that during the nortli- 

 east monsoon, if the winds which blow the waters down the Bay, be more than usually moderate, and 

 the moon's parallax be high, there may be a high tide, and with it a bore, and this, agreeably to the 

 third local cause, will happen at night. These night bores are particularly dangerous, as they are 

 very rare and, consequently, unexpected. They may be guarded against, by always considering it 

 possible for therato occur during the north-east monsoon at night, upon a high parallax of the moon. 

 Agreeably to the same local cause, it is fortunate that the bores at night, during the south-west 

 monsoon, are not so high, as in the day. 



