Volume II Part 24 (1/2)

The lifted heavy cold air over a heated country becoht, the heaviest part descends first, and the rest follows iusts after heats, and hurricanes in hot clih in hot cli fro froion full of watery particles, condenses them, renders the soe and extensive; soradually increasing; the cold edge or surface of the cloud condensing the vapours next it, which form smaller clouds that join it, increase its bulk, it descends with the wind and its acquired weight, draws nearer the earth, grows denser with continual additions of water, and discharges heavy showers

S in a clear sky, in hot climates portend storms, and warn sea on its axis in about twenty-four hours, the equatorial parts must move about fifteen miles in each radually less to the poles, and there nothing

If there was a general cal in every part as fast as the earth or sea it covers

The air under the equator and between the tropics being constantly heated and rarefied by the sun, rises Its place is supplied by air fro from parts wherein the earth and air had lessthe quickerard; the earthunder the air[37]

[37] See a paper on this subject, by the late ingenious Mr Hadley, in the Philadelphia Transactions, wherein this hypothesis of explaining the tradewinds first appeared

Thus, e ride in a calainst us: if we ride with the wind, and faster, even that will seeainst us

The air rarefied between the tropics, and rising, ion north and south Before it rose it had acquired the greatest ree of this her latitudes, where the earth'stowards the equatorial parts, to supply the vacancy occasioned by the air of the lower regions flowing thitherward

Hence our general cold winds are about northwest, our suusts the sah not cloudy, has a kind of haziness in it, which makes objects at a distance appear dull and indistinct This haziness is occasioned by the great quantity of moisture equally diffused in that air When, by the cold wind blowing down a it, it is condensed into clouds, and falls in rain, the air becousts, distant objects appear distinct, their figures sharply tereal the surface of the earth by carrying off its fire War over that frozen surface will be chilled by it Could that frozen surface be turned under, and warmer turned up from beneath it, those inds would not be chilled so much

The surface of the earth is also someti changed, heats the air that reat bodies of water, agitated by the winds, continually change surfaces; the cold surface in winter is turned under by the rolling of the waves, and a warmer turned up; in summer the warm is turned under, and colder turned up Hence the more equal temper of seawater, and the air over it Hence, in winter, winds from the sea seem warm, winds from the land cold In summer the contrary

Therefore the lakes northwest of us,[38] as they are not so much frozen, nor so apt to freeze as the earth, rather moderate than increase the coldness of our winter winds

[38] In Pennsylvania

The air over the sea being warhter in winter than the air over the frozen land, eneral northinds, which blow off to sea at right angles fro, the heavy, cold land-air pressing into its place

Heavy fluids, descending, frequently form eddies or whirlpools, as is seen in a funnel, where the water acquires a circulara vacancy in thedoard, like a speaking-tru, s, the parts of air acquiring a circularfro there a vacancy; if descending, greatest above and lessening doard; if ascending, greatest below and lessening upward; like a speaking-truround

When the air descends with a violence in some places, it may rise with equal violence in others, and forevery way from the centre or axis of the truh the sides, the whirling air, as an arch, preventing; it reatest pressure inward ht of the surrounding at, rises within, and carries up dust, leaves, and even heavier bodies that happen in its way, as the eddy or whirl passes over land

If it passes over water, the weight of the surrounding atmosphere forces up the water into the vacuity, part of which, by degrees, joins with the whirling air, and, adding weight and receiving accelerated motion, recedes farther from the centre or axis of the trump as the pressure lessens; and at last, as the trump widens, is broken into small particles, and so united with air as to be supported by it, and become black clouds at the top of the trump

Thus these eddies may be inds at land, water-spouts at sea A body of water so raised th to support it, or the whirling arch is broken so as to ad in the sea, it is harressive motion of the whirl it has moved from the sea over the land, and then breaks, sudden, violent, and mischievous torrents are the consequences

_To Dr Perkins_