Prof. Hare on Gales in the Atlantic States of N. America. 111 
as denser by the cold, consequent to its remoteness from the 
earth—and another may be as much denser by the increased 
pressure arising from its proximity to the earth, as rarer, by 
being warmer. Hence when unequally heated, different strata 
of the atmosphere do not always disturb each other. Yet after 
a time, the rarefaction in the lower stratum, by greater heat, 
may so far exceed that in an upper stratum, attendant on an 
inferior degree of pressure, that this stratum may preponderate, 
and begin to descend. Whenever such a movement commences, 
it must proceed with increasing velocity ; for the pressure on 
the upper stratum, and of course its density and weight, in- 
creases as it falls; while the density and weight of the lower 
stratum must lessen as it rises. Hence the change is at times 
so much accelerated, as to assume the characteristics of a tor- 
nado, squall, or hurricane. In like manner may we suppose 
the predominant gales of our climate to originate. Dr. Franklin 
long ago noticed, that north-eastern gales are felt in the south- 
westernmost portions of the continent first; the time of their 
commencement being found later, as the place of observation 
is more to the windward. 
The Gulf of Mexico is an immense body of water—warm, 
in the first place, by its latitude,—in the second place, by its 
being a receptacle of the current produced by the trade-winds, 
which blow in such a direction as to propel the warm water of 
the torrid zone into it, causing it to overflow and produce the 
celebrated Gulf stream, by the ejection, to the north-east, of 
the excess received from the south-east. This stream runs 
away to the northward and eastward of the United States, pro- 
ducing an unnatural warmth in the ocean, as well as an im- 
petus, which, according to Humboldt, is not expended until 
the current reaches the shores of Africa, and even mixes with 
the parent flood under the equator. The heat of the Gulf 
stream enables mariners to ascertain by the thermometer 
when they have entered it: and in winter, this heat, by in- 
creasing the solvent power of the adjoining air, loads it with 
moisture—which, on a subsequent reduction of temperature, 
is precipitated in those well-known fogs with which the north- 
eastern portion of our continent, and the neighbouring seas 
and islands, especially Newfoundland and its banks, are so 
much infested. An accumulation of warm water in the Gulf 
of Mexico, adequate thus to influence the ocean at the distance 
of two thousand miles, may be expected, in its vicinity, to have 
effects proportionally powerful. The air immediately over the 
Gulf must be heated, and surcharged with aqueous particles. 
Thus it will become comparatively light: first, because it is 
comparatively warm; and in the next place, because aqueous 
vapour, 
