336 Cyclones. 



received in the funnel of the rain-guage, which therefore 

 collects both spray and rain. It is observed, apparently in 

 support ofi;his explanation, that drops of water which fall 

 down the shafts of deep mines gradually increase in size as 

 they descend, until they reach the bottom of the shaft. This 

 is probably owing to spray from other broken drops attaching 

 itself to the drops as they descend. 



To return, however, from this digression, suggested by the 

 power of the wind upon the sea, a few instances of great 

 inundations in a cyclone may be noticed here, as illustrating 

 still further the force of the wind. The low-lying plains of 

 Bengal, defended by dykes like those of Holland from sudden 

 incursions of the sea, are frequently exposed to the attacks of 

 the storm-waves of cyclones. Calamities on this coast are 

 frequent, chiefly from, the destruction or insufficiency of the 

 dykes. Burrisal, at the mouth of the Ganges, was thus 

 overwhelmed in the month of June, 1822 • Balasore, at the 

 mouth of the Hooghly, in October, 18-31 ; and, again, Balasore 

 and Hidgelee were completely destroyed, on the 21st of May, 

 1833, by a storm-wave which rose twelve feet above the 

 ordinary level of the tide. Calcutta, on the 5th of October, 

 1864, suffered in its turn. The centre of a cyclone passed 

 that day directly up the Hooghly, and caused an inundation, as 

 well as ravages upon its banks, more fearful than any pre- 

 viously recorded in the history of this kind of storm. 



The storm- wave, raised by the force of the wind upon a 

 lee-shore, is in the open ocean impelled in all directions from 

 the centre of a cyclone, and is felt at a distance of even 1000 

 miles as a swell upon the sea. A surf breaks upon the reefs, 

 and a swell rises one or two feet at the Bermudas, at the 

 passage of every West Indian hurricane near its coast. This 

 disturbed appearance of the sea is accordingly a useful 

 indication of the neighbourhood of a revolving storm, either 

 approaching, or receding, or traversing the ocean, at a 

 distance. 



It is important to notice that a depression of the barometer 

 invariably accompanies the passage of the centre of a cyclone. 

 Sir William BeicL notices an instance of a typhoon, which 

 traversed Macao on the 5th of August, 1835 ; in which the 

 barometer fell a full inch and a half at the passage of the 

 centre; while at Canton, not quite sixty miles north from the 

 track of the storm's centre, the oscillation of the mercury was 

 little more than three-tenths of an inch. A number of similar 

 cases are brought forward by Piddington, who distinguishes 

 two classes of cyclones. In one of these, or storms of gentle 

 depression, the mercury descends one or two tenths of an inch 

 an hour, until the centre is near, when it remains almost 



