412 
WINDS AND STORMS. 
3rd. There is in all latitudes (a few trades oflimited extent where 
local causes have a decided effect excepted) a predominance of winds 
blowing from the poles towards the equator, over those moving in 
the opposite direction, but this predominance is not so well marked 
and decided as that of the westerly over the easterly winds, between 
the latitudes of 30 and 60 degrees. 
4th. D uring the warm weather within the temperate, and at all 
seasons within the limits of the torrid zone, the fall of rain is often 
accompanied by lightning, thunder, and violent winds, constituting 
what is commonly called a thunder-storm. Thunder-storms gene¬ 
rally commence between mid-day and sun-set, and move from west 
to east. 
Other general facts might be added, but these are such as require 
to be viewed in connexion with the laws which regulate the move¬ 
ments of the aerial currents over the surface of the globe, and the 
origin of those currents are to be investigated. The truth of the 
statements contained in these propositions will first be shewn, after 
which an inquiry will be instituted respecting the causes by which 
the facts asserted in them may be supposed to be produced. 
1. That part of the great ocean which lies between the thirtieth 
parallel of latitude on both sides of the equator, is constantly swept 
by a wind varying but a few points from the east. The direction, 
velocity, permanence, and other characters of the trade-winds, are 
too well known to require any particular remark. They are affected 
by a number of local causes. Near the equator they blow from the 
east point, but at a distance from it. Their course becomes inclined 
lo the parallels of latitude, so as to be at length from the north-east 
and south-east, near their northern and southern limits. Their 
force and direction are also influenced by the proximity of islands 
and continents. Along the western side of Africa their direction is 
reversed ; to the distance seaward of about three hundred miles, they 
blow towards the land, and nearly at right angles to the coast. 
Halley notices a tract between the fourth and tenth degrees of north 
latitude, and the longitudes of seventeen and twenty-three degs. 
wherein it were improper to say shore is any trade-wind, or yet a 
variable one, for it seems condemned to perpetual calms, attended 
with terrible thunder, lightning, and rains, so frequent that our na¬ 
vigators call this part of the sea the rains. The little winds they 
have are only some sudden uncertain gusts of very short continuance 
and less extent, so that sometimes each hour there is a different gale, 
which dies away into a calm before another succeeds; and if a fleet 
of ships be in sight of one another, each will have the wind from a dif- 
