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body against which, what I may term the rays of found, ftrike, and unable to pafs through it, are beaten back, and returned. This returning may arife from many kinds of objects, from a wall, from a hill, or if other impediments to the progrefs of found be wanting, the atmosphere furnishes clouds, which often create echoes to great founds. There are many very curious echoes mentioned by authors; fome natural, fome artificial; in fome, the found is repeated twenty, thirty, even fifty times, fome repeat fyllables, and fome words, or short sentences; this is easily accounted for on the principles just hinted,

We fhall turn our thoughts for a moment to the ufes of the atmosphere as they regard the fenfe of SMELLING. We may confider a flower, or other odoriferous body, as a centre from whence are diverged thousands of powerful and active atoms, which, when they meet our olfactory nerves, excite a fmell, of whatever nature it may, pleafant or foetid, agreeable or offenfive. Thefe atoms, or particles, are received into the atmosphere, where they float, and whereby they are distributed far and wide, Perhaps, I may, illuftrate the share of the atmosphere this bufinefs, by referring you to a bafon of clear water, in which if you drop a little coloured liquor, the water, foon becomes tinged, and the colour of the liquor fpreads through the whole; attenuated, weakened, and thinned; which effect, no doubt, takes place on a larger fcale in the atmosphere with regard to odoriferous particles; and very much to our benefit, fince we well know, that many fmells are too ftrong to be endured without inconvenience; that fome are fatal though fragrant, because undiluted (witness

the

the pea-bloffom, damp of mines) and that most are unhealthy if too conftantly reforted to. The tea-brokers in London (who judge of tea by fmelling it ftrongly) are greatly liable to the palfy; and the perpetual use of perfumes, among the women of Chili, produces an internal disease, as dreadful as incurable. But when a free circulation imbibes fragrance, or when fragrance is in its nature moderate, then it conduces to health and cheerfulnefs, refreshes the fpirits, and exhilarates the fenfations; fuch is the fmell of morning and evening, arifing from vegetation; fuch is new mown hay; and many others, which are happily no ftrangers nor rarities among us.

See from one fimple covering furrounding our habitation, what various fervices are bestowed on the children of men;

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what various fervices which come to our knowledge; but could we fee the magazines of snow, the treasures of hail, the repofitories of froft, the refervoir of the drops of the dew; could we trace the fprings and circulations of the electric fire, of the magnetic fluid (at which we can but guefs); could we defcend to the minutiae of thofe proceffes conftantly in motion, whereby vegetation is advanced, fertility increased, life prolonged by refpiration, and many other beneficial effects produced, we might justly lay our fingers on our lips in adoring filence, and mufe that praife to which expreffion is inadequate.

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PLATE I.

F

IG. 1. represents a general idea of the benefits resulting to the earth by the intervention of an ATMOSPHERE, This is fuppofed to be the northern hemisphere; the north pole in the centre of the figure; the Sun in the equator, confequently the Equinox.

It appears by the figure, that those parts which have lately,
by the diurnal rotation of the earth, turned from the fun,
and are lofing fight of him (i. e. the part marked Evening),
yet enjoy his beams by the refraction of the atmosphere:
were no fuch medium around it, a would be involved in
night; whereas, night is but just fenfible at d, and the in-
terval between thofe letters, is gradually preparing for the
total absence of the folar luminary. At Noon the atmof
phere fpreads the rays of light all around, and diffuses
equal and general brightness. In Morning, as the parts
of the globe, b and c, turn toward the fun, the light gradu
ally advances, fo that, although in ftri&tnefs only b should
be illuminated, yet the atmosphere extends the folar rays to
c, and prepares those
parts for perfect day. Thus it ap
pears, that though the line a b, fhould be the natural boun
dary of day and night, yet by this invaluable contrivance,

much

ATMOS

ат

TWILI

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