198 DOVE ON THE LAW OF STORMS. 
whalers when in high latitudes. In the regions of the trade — 
winds, and of the monsoons, the numerous examples of greatly 
diminished pressure ushering in the typhoons and West India 
hurricanes are well known. ; 
[M. Dove then proceeds to recount several such instances. 
In 1837 the Harbour Master at Porto Rico warned the ship-_ 
ping in the port to prepare against a storm, as the barometer 
was falling in an unusual manner; at 8 p.m. the preceding even- 
ing it had stood at 333!"28, and had sunk to 315!"27. The 
precautions taken were unavailing ; thirty-three vessels at anchor — 
were all destroyed, and at St. Bartholomew alone 250 buildings 
were overthrown. At the same time the barometer fell at St. 
Thomas from 337" to 316", and the ravages of the hurricane 
were even greater than at Porto Rico. He describes the violent 
effects of the wind on this and other occasions, in the destruction 
of vessels in harbour, forts, houses, and larger buildings ; in drag- 
ging large guns (twenty-four pounders) along the ground; dri- 
ving boards through trees and walls several inches in thickness, 
&c. &c. He refers also to General Baudrant’s account of the 
destruction of Basse Terre in Guadaloupe by a hurricane in 
1825; and to hurricanes in 1828 and 1836 in the island of Mau- 
ritius, where in 1828 the barometer fell to 316!, and in 1836, 
having stood at 337!"00 at 5 a.m. on the 6th, it had fallen 
to 317"-85 at 8 a.m. on the 8th. M. Dove says further in a 
note, “ A striking instance of the great mechanical power, even 
of smaller hurricanes, occurred near Calcutta in April 1833, 
when a revolving storm, not above half an English mile in 
breadth, passed between Calcutta and the great salt water lake 
three miles to the east of that city, and in the space of four hours, 
on a track of sixteen miles in length, caused the death of 215 
human beings, and injured 223. It overthrew 1239 fishermen’s 
huts; a bamboo was driven quite through a wall of five feet 
thick, piercing the covering of masonry on both sides, so that 
the Editor of the Indian Review says a six-pounder would scarcely 
have had the same effect.” | 
If two phenomena frequently occur together, we may surmise, 
with some degree of probability, that they have a causal con- 
nexion; but it may remain quite undecided which is the con- 
ditional, and which the contingent phzenomenon ; or both may 
be effects of a third phenomenon, which is itself their common 
cause. Further, if one of the phenomena be really an immedi- 
