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Show [ II4 ] -Thick as the dews, which deck the morning Rowers, Or rain-drops twinkling in the fun-bright Jhowers, Fair Nymphs, emerging in pellucid bands, Rife, as fhe turns, and whiten all the lands. 10 I. " YouR buoyant troops on dimpling ocean tread, Wafting the moift air from his oozy bed, Ao_uATIC NYMPHs !-You lead with viewlefs march The winged V a pours up the aerial arch, On each broad cloud a thou:fand fails expand, And fleer the iliadowy treafure o'er the land,, 'The winged vapours. I. 14. See additional note, No. XXV. on evaporation. On each broad doud. 1. I 5· The clouds con !Ill: of condenfed vapour, the particles of which are too fmall feparately to overcome the tenacity of the air, and which therefore do not ~efcend. They are in fuch fmall fpheres as to repel each other, that is, they are applied to eac~ other by fuch very fmall furfaces, that the attracrion of the particles ?f ea~~ ~rop to its own centre is greater than its attraaion to the furface of the drop in Its V!C1111ty; every one has obferved with what difficulty fmall fpherules of qui ck!l lver can be made to unite, owing to the fame caufe; and it is common to fee on riding through ihallow water on a clear day, numbers of very fmall fpheres of water as they are thrown ~rom the horfe's feet run along the furface for many yards before they again unite with It. In many cafes thefe fpherules of water, which compofe clouds, are kept from uniting by a furplus of elecrric fluid ; and fall in violent fhowers as foon as that is withdrawn from _the~, as in thunder fiorms. Sec note on Canto I. 1. 55'4· If m.ti11S fiate a cloud becomes frozen, it is torn to piect's in its defcent by the fricrion of the air, and falls in white flakes of fnow. Or thefe flakes are roumle.J by being rubbed [ liS ] Through vernal fkies the gathering drops diffufe, Plunge in foft rains, or fink in filver dews.- together by the winds, and by having their angles thawed off by the warmer air beneath as they defcend; and part of the water produced by thefe angles thus diffolved is abforbed into the body of the hailfl:one, as may be feen by holding a lump of fnow over a candle, and there becomes froz en into ice by the quantity of cold which the hailfione poffefles beneath the freezing point, or which is produced by its quick evaporation in falling; and thus hailltones are often found of greater or lefs denfity according as they con!ifi of a greater portion of fnow or ice. If hailftones con!lftecl of the large drops of iliowers frozen in their defcent, they would confift of pure tranfparent ice. As hail is only produced in fummer, and is always attended with fiorms, fome philofophers have believed that the fudden departure of electricity from a cloud may effect fomething yet unknown in this phenomenon; but it may happen in fummer independent of elechicity, becaufe aqueous vapour is then raifed higher in the atmofp!Jere, whence it has further to fall, and there is warmer air below for it to fall through. Or fink infilver dews. 1. 18. During the coldnefs of the night the moifiure before diffolved in the air is gradually precipitated, and as it fubfldes adheres to the bodies it falls upon. Where the attraction of the body to the particles of water is greater than the attraClions of thofe particles to each other, it becomes fpread upon their furface, or Oides down them in aClual contact; as on the broad parts of the blades of moift grafs : where the attratlion of the furface to the water is lefs than the attraCtion of the particles of water to each other, the dew fiands in drops; as on the points and edges of grafs or gorfe, where the furface prefented to the drop being fmall it attracrs it fo little as but jufi to fupport it without much changing its globular form: where there is no attracriou between the vegetable furface and the dew drops, as on cabbage leaves, the drop does not come into contact with the leaf, but hangs over it repelled, and retains its natural form, compofed of the attraction and preffure of its own parts, and thence looks like quickfllver, reflecring light from both its fnrfaces. Nor is this owing to any oilinefs of the leaf, but fimply to the poli!h of its furface, as a light needle may be laid on water in the fame manner without touching it; for as the attractive powers of polifhed furfaces are greater when in acrual contaa, fo the re,plllfive power is greater before contaCt. Q.2 |
