14. EF. Loomis— Observations of the U. 8. Signal Service. 
the low area was stronger than the huge wind which pre- 
ceded it. This result, a believe, accords with what has gener- 
ally been observed in ‘tropical cyclones, and appears to suggest 
the explanation of the origin of the cyclone, and the direction 
of its progressive movement. The prevalent direction of the 
wind in the neighborhood of the West India Islands, is from 
the northeast. Occasionally a strong wind sets in from a south: 
erly quarter. The interference of these winds gives rise to a 
gyration, and sometimes rain-fall is the result. hen rain 
commences, the latent heat which is liberated, causes the wind 
to flow in from all quarters, by which the rain-fall is increased ; 
and since the winds are deflected by the rotation of the earth, 
an area of low pressure is produced, and the force of the winds 
is maintained as long as the rain-fall continues. The effect of © 
this strong wind from the south is to transport the low center — 
in a northerly direction; and by the combined action of this 
south wind and the normal wind from the northeast, the center 
of low eigen: is usually carried in a direction between the , 
north and west. 
The following roimat presents some of the results derived 
from this investigatio 
. The 
lowest auteds in which, a cyclone has been found | 
near the “West India Islands is ten degrees, and the lowest lat: 
itude in the neighborhood of Southern Asia is six degrees. 
Violent squalls and fresh gales of wind have however been 
encountered directly under the equator. 
2. The ordinary course of tropical hurricanes is towards the 
west-northwest. Ina few cases they seem to have advanced 
towards a ace a little south of west, and in a few cases their : 
course has been almost exactly towards the north. 
at On See We ee 
3. Tropical hurricanes are invariably accompanied by a vio- 
lent fall of rain. This rain-fall is never less than five inches io — 
twenty-four hours for a portion of the track, and frequently it 
exceeds ten inches in twenty-four hours. 
4, Tropical storms are. generally preceded by a northerly | 
wind, and after the passage of the low center the wind gener 
ally veers to the southeast at stations near the center ; and the — 
southerly wind which follows the low center is generally 
stronger than the northerly wind which preceded it. This fact 
appears to suggest the explanation of the origin of the cyclone © 
and the direction of its progressive movement. 
5. None of the storms which have pursued a southeast cours? 
across the United States and its vicinity, have been tra 
further south than latitude 224 degrees, and only three havé 
been traced as far south as latitude 25 degrees. These storms 
during their progress southward generally decline in intensity: 
Somie of them decline to such an extent that their course cat 
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