LECTURE IX.

A

MIXTURE of good and ill, characterises the present state; our benefits are alloyed with attendant evils; and grateful alleviations accompany forrows. On this terrestrial globe, life, pleasure and delight, are brothers to death, anguish and mifery. Ever various, the mantle which furrounds our habitation! it is now replete with elegance and falubrity, is the fplendid robe of royal magnificence: prefently, behold darknefs and gloom terrific! flaming fire devours, thunder shakes the earth, the torrent pours its rapid force, or hail defcends in dreadful volleys, or the whirlwind fpreads fweeping devastation. -Is the deluge paft? The reverfe is equally fatal:-the Heaven with-holds its rain, no gentle dew defcends, no cooling fhowers; "the heavens above are iron, the earth beneath is brafs," "the cattle forfake the field where they drop their young; the hufbandman covers his head, defponding for his tillage; the nobles fend their little ones to the waters, they come to the pits; but return with empty veffels, afhamed, confounded, and covering their heads." Or, inftead of health, the atmofphere diffufes mortality; flight is vain, the contagion overfpreads a country! remedy is vain, we breathe the peftilence !-No longer a fplendid robe; our mantle is now the en

VIII.

M m

venomed

venomed garment which confumes the vitals of the wearer. Happy Britain, which only by report conceives of thefe calamities, and only by fympathy fuffers thefe miferies! To us fuch defolation is unknown :-yet we should never forget that period when London was verdant with grass, for want of pas fengers to tread the streets.

But at this time, LADIES and GENTLEMEN, the atmosphere which furrounds us is to be confidered with regard to thofe operations which are conftantly carrying on in it, and which more immediately strike our obfervation as belonging to the subject. Firft, we treat of WINDS; and thefe we fhall divide into CONSTANT, and INCONSTANT.

When I attribute conftancy to the wind, I am aware that I feem to contradict daily experience; to this I reply, we must not fo depend even on experience itself, as to exclude facts which oppose it for though among us the vane is no emblem of steadiness, till "it ruft to a point, and fix at laft," yet, in the proper latitudes of the Pacific ocean, the wind blows steady, in one uniform direction, and with one continued velocity; the feaman fets his fails, and almost forfakes the helm; night and day the breeze fwells his canvafs, and wafts his veffel in full security; the wide-extended waters fear not tempeft or ftorm; never deformed by contending billows. Such is the description of fome parts of the great fouth fea.

There is something striking, to this purpofe, in Commodore ANSON'S Voyage in the fouth fea. We read, at one part, of raging waves beating the fcarce floating fhip, raifing

her

her now mountain high, then plunging her deep into the abyss, the veffel pitching, toffing, ftruggling with the ftorm; the wind quivering the mafts, and rending the fails; cold, rain, snow, hail, in furious union combating the adventurous navigator, whofe frozen limbs almost forego their life. Afterwards, we read of weather which permitted every fail abroad, and wafted them fafely across the immense Pacific.—In fact, vesfels going with the breeze, ufually make their passage in fix or feven weeks, while others going the contrary way, are obliged to avoid the limits of the trade-wind, and employ not less than fix or seven months. Such is our account of Conftant Winds, which alfo blow in the Atlantic and Ethiopic oceans with equal permanency.

There are alfo Winds of contradictory Conftancy: I mean, which one part of the year blow with fettled regularity in one direction, the other part of the year they blow with equal fteadiness from an oppofite point.. Thefe are termed Monfoons, from a pilot of that name, who firft adapted them to the purposes of his navigation.-The interval between the changes of the Monfoons is the feafon of tempeft, and is termed the breaking up of the Monfoons.-Thefe winds have their stations, and are bounded often by a projection of land, as peninsular India, on one fide of which the coafts are haraffed with hurricanes, on the other they never know them.

As thefe winds occupy the moft confiderable part of the globe, we shall here endeavour to explain their caufes.

Of the trade-wind we obferve, that it reigns, where reigns the greatest folar heat, i. e. at, and adjacent to, the Equator;

we have already noted the ardour of the fun in these parts, and it should feem, that his fiery beams by rarifying the air, and by heating the earth, caufe a perpetual vacuity in the ad jacent atmosphere; to fupply this vacuity, the air from all quarters rufhes with proportionate velocity. If you please, we will examine this matter fomewhat more clotely: for a moment we fuppofe ourselves beneath the line; at noon the fun is vertical, and darts his perpendicular rays with intenfe fervor; the air around us feels this fervor, and expands on all fides, it widens, it spreads, it recedes from this fcarce-fuftainable heat; thus equally expanded it will continue while the fun is high; but when he declines, the expantion declines alfo in that quarter which he forfakes (i. e. the East), and thereby, fuch quantity of atmosphere as lately occupied very confiderable space, is now contracted into fmaller dimenfions, and leaves a void—which void is regularly fupplied from whereever the air can fupply it. As the daily progrefs of the fun is from east to weft, this supply of air will follow the folar progrefs; i. e. will blow from the eaft; and, I apprehend, were no impediment interpofed, this eaft wind thus following the fun, would be violent: but we must regard, as one bar to its violence, that heat which remains in the earth after the fun has quitted it; for the earth being a denfe body, retains heat in great quantity, and this it continues to emit, in proportion as the atmosphere shews any difpofition to refrigeration. Thus it appears thefe parts of the atmosphere are conftantly heated-exceffive hot at noon, little lefs in the evening, and at night are far from temperate.

I might