Meteorological Sketches. 53 
of the latter are mainly horizontal, or parallel to the earth’s surface. 
Notwithstanding this, the common theory of winds supposes a con- 
stant rising of the atmosphere in the equatorial regions, connected 
with a flow in the higher atmosphere towards the polar regions, and 
a counter flow at the surface towards the equator, to supply the as- 
cending current. This ascending movement, however, has never yet 
been discovered, and it is easy to perceive that if it existed in the man- 
ner supposed, its magnitude and velocity must be altogether too great 
to have eluded observation. 
It is apparent, however, that different currents often prevail at dif- 
ferent altitudes, superimposed one upon another, and moving at the 
same time in different directions. These currents are often of different 
temperatures and hygrometrical condition, and are found moving with 
different degrees of velocity. It is by the influence of these currents 
that volcanic ashes, and other light substances, which are elevated by 
means of volcanic spouts or whirlwinds to the higher regions of the 
atmosphere, are conveyed to great distances, and in directions which 
are often contrary to the prevailing wind at the surface. On the 
eruption in St. Vincent, in 1812, ashes were thus deposited at Bar- 
badoes, which is 60 or 70 miles to the windward, and also on the 
decks of vessels still farther eastward, while the trade wind was 
blowing in its usual direction. On the great eruption of the volcano 
of Cosiguina, on the shores of the Pacific, in Guatemala, in Jan- 
uary, 1835, the volcanic ashes fell upon the island of Jamaica, at 
the distance of 800 miles in a direct line from the volcano. Facts 
like these ought to put at rest the common theory of the trade winds, 
according to which these ashes would sooner have fallen upon the 
northern shores of the Gulf of Mexico, or the peninsula of Florida. 
On the same occasion the volcanic ashes were also carried westward 
in the direction contrary to the trade wind on that coast, and fell up- 
on H. M. ship Conway, in the Pacific, in lat. 7° N., long. 105° W., 
more than 1,200 miles distant from the volcano, in the direction 
which is nearly opposite from that of Jamaica. ‘These phenomena 
were doubtless the effect of two different currents prevailing at dif- 
ferent elevations ; but we shall seek in vain, in these developments, 
for proof of the commonly received but imaginary system of the 
trade winds. 
The occasional interposition of a warmer current of atmosphere 
between the lower current and the higher regions, has been proved 
by the observations of aeronauts. In countries situated like the Uni- 
