110 REPORT—1840. 
tion of the courses of many hurricanes recorded in ships’ logs, 
which he has projected on excellent charts. The theory of 
Colonel Capper proposed for the storms of the eastern hemi- 
sphere is found to be not less applicable to the terrific tem- 
pests of the West Indies, where these gyratory movements ap- 
pear commonly to take their rise, invariably revolving from 
right to left, which at the same time progress in a straight 
or curved path, usually occupying a space of from 100 to 500 
miles in diameter. These rotatory movements commence in 
tropical latitudes usually near the West India Islands; they 
move at first in a westerly and continually more northerly di- 
rection, until they reach a latitude of about 30°, when they turn 
rather abruptly towards the north-east. It is impossible not to 
believe that the path of these storms is mainly determined by 
the configuration of the American continent *. 
213. The fall of the barometer, especially near the central 
parts of the storm, is accounted for by the action of centrifugal 
force. 
214. It is very evident that the direction of the wind to a sta- 
tionary observer, whilst one of these vortices is passing over 
him, will vary in a manner depending on his position with respect 
to the axis of the storm. If the centre pass rigorously over his 
station, he will experience a gale first in one direction and then 
in a directly opposite one, without any intermediate points of 
the compass; as an observer is stationed on one side of the axis 
or the other, a little reflection will clearly show that the appa- 
rent change in the wind’s direction will follow opposite courses 
in the one or other position. This and many other deductions 
are fully made by Redfield and Reid; we only mention it just 
now in order to point out that this, at all events, must be con- 
sidered an essential exception to Dove’s law of rotation. 
215. There is, however, a remarkable analogy to Dove’s law 
in one respect, which is, that the direction of rotation of storms 
is opposite in the two hemispheres, being right-handed in the 
southern. This important fact was deduced by Redfield from 
his hypothesis that storms are produced by the mingling and 
collision of the superior equatorial stream with the polar stream 
or trade winds. Colonel Reid has given great support to this 
view by tracing some storms of the southern tropical regions. 
216. Not the least important and interesting part of this in- 
quiry is the deduction of practical rules for steering out of in- 
stead of into these vortices, an application distinctly pointed out 
by Col. Capper as well as his successors ; but this does not con- 
cern us at present. 
* See Colonel Reid’s Charts, iii., v., vii. 
