Meteorological Sketches. 61 
any important change. Owing to this fact, observers sometimes be- 
lieve that they witness the commencement of a water-spout, or tor- 
nado, when the same has previously been in action for one or more 
hours, and when the cloudy pipe or pillar happens to disappear, the 
spout is supposed to have ‘ burst,’ while, often, it has undergone no 
important change, except, perbaps, a slight decrease in its activity. 
The active and violent portion of the whirlwind surrounds the spout 
invisibly, and is probably of much greater diameter at a distance 
from the surface of the earth than at the base of the spout. Thus, 
when a spout or whirlwind has passed near a ship, the upper spars 
have been converted into wreck while no violence of wind was felt 
on the 
Water-spouts follow the course either of the surface wind or of the 
higher current with which they may communicate, or their course, 
may be modified by both these influences without being absolutely 
determined by either. They abound most, however, in those calm 
regions which are found at the external limits of the trade winds, 
and in the regions near the equator. 
It bas been common to ascribe whirlwinds and water-spouts, as 
welt as larger whirlwind storms, to an impulse produced by the 
meeting of contrary currents, but the laws of distribution and of mo- 
tion in an oceanic body, are such as do not permit the movements 
of its different currents and gyrations to meet in conflict with each 
other; besides, any conflicting movement in the air would necessa- 
rily produce a rise in the barometer, whereas it is generally known 
to fall at the commencement of a storm or whirlwind, either of large 
or small extent. We may observe, also, that whirlwinds and spouts 
appear to commence gradually, and to acquire their full activity 
without the aid of foreign causes ; and it is well known that they are 
most frequent in those calm regions where, apparently, there are no 
active currents to meet each other, and they are least — where 
currents are in full activity. 
Of Trade Winds and the circuitous Character of the Atmospheric 
urrents. 
It is found that in almost every country, and in every sea, the 
wind is more or less predominant in a particular direction. In open 
sea, between the equator and the 30th parallel of north and south 
latitudes, the wind, for the most part, blows from the eastward; but 
near the eastern borders of any ocean, below these latitudes, the 
