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512 Of a Czflzz/atiwz (yr humid 11/2: in Nov. 1776, when eroding it in his voyage from Philadelphia to France. 1:0, though the fides and bottom of this great Watcr-ctrrrt‘nt undoubtedly .lofe heat, by mixtng wtth colder \v":. s ;. yet the inner parts (not ["113 able to C091 Md" WM") "6‘5"" tl‘F" heat "IUCll longer; and in fact, as Dr. Franklin has {at-the. oblervetl, preferve a coniiderable [hare or it up to the banks of N‘mvfonndland.‘---g". How {lowly/frantic" operates here, appears lrom confidcrti t; that this water-current travels only at the mm of five or fix miles an hour in ,1". gulph itfelt', and at about [mi miles an hour perhaps near \"irgini ; becoming not only limw-ra it goes on, lint thinner Circulation of humid Air. 513 the tiling air can 10/? in 5121!; there being none that are mafi‘y in {a rare a medium, and the lighter ones may poflihlv be thoutrht by this period of time proportionably litturated with heat. oto°."l‘he particles ofair as foon as they become cold, appear to drfmm'; not to rile again, till again properly heated: and thole that were fore cold, never rife while they continue {0 : And the winds uh i. blow up to the poles, ifthey continue to blow on, mull turn the poles and blow down into milder latitudes-I I°. The atmofphere being much the denfeli. near the earth, whatever warms the flrfi (i. e. thallower) and broader allii in {nrlacm and yet the dillanee to Newfoundland is in all perhaps tgco .nles. The farm concluiion is to be drawn from the {en's remainiu liquid, or at 28'; of hcafl, three or four miles in depth, reckoned from the furfaee, warms [in/fat the twin/2 mafi 1f air furrounding the globe-120. But if notwithll‘anding this, (and what Dr. Franklin has {aid in p. 197-8. very high upin thcpolar circles, and within 12 or 13 degrees of the ofhis Letters,) there be thought no {ueh circulation in the atmofphere pole to the north : And thy lame appears from hot bla ting 1~ winds being found at a great difianee twin the places when: they are formed; and the lame, from many of our cold \xind..--6'. The .u‘iual warmth and moillure of the higher air in the tropics, is {een from clouds (or uncondenfed vapour) often exhinq at much 115 above defcribed; then we may {till i."PPOfe that moill heated Ril‘ may rife or be moved forwards at certain feafons from the more tfiflpil‘flh' latitudes. The heat of jamaica is rarely equal to that oceafionally known at I'eterlburgh: And Dr. Franklin's theory is more interelled in the event towards the pole, than in fixmg the origin at the equator.---t3°. What is {aid here of the northern he- mifphere, applies, mutatir rzzulandix, one may {uppofe to thefiutbern ; ‘greater heights, than thofe at which mountains, from their litu- ution, remain perpetually covered more or lcfs with fnows; and .the fame appears alfo in the lower air in the northern regions, for if the fun's heat penetrates let's on that fide the line, the cold when ice-mountains there find means to condenfe local fogs and clouds out of the air around them. 7". The mafs of warm air coming from the equator may, from the lots at its edges, ihrinl: there extends to much farther from the pole: 55C: and ‘UW wrm‘ *15-] much in general fize; and yet, as it had filled the larger degrees of longitude at the equator, ilill occupy great proportional room in the {mailer degrees of longitude at the pole. --«-- 8 . The [ § 14. " The_ earth, in and warm climates, is ge-n ‘ _ temperate _ . " nerally fitto receive eleé'trtcttylln-king {uddenly From the'clouds: 01‘ {frhflt lhould be ‘00 (50' at WP: 1‘5 waters, ""5: butldmgS. 34C- Jinfate of we earl/2 in the polar (il'rlfl being only about 7‘... part of which reach down to the morlier parts. E.] what the temperate and tropical zones contain, the mafs of cold air there will be found {maller upon comparifon than ful'peé‘ted; and confirm {eélion 6, particularly when it is confidcred, that though thefe parts of the tart/2 are placed for fuch long periods immoveably in the fhade, yet the air above them is very fluctuating, new fuc- ceflions of it pouring in on every fide from parts that are more en- lightened-9°. It would be well to confider to tux/mt had/u above, ‘ [At this degree Mr. Nairne has found that/ea water begins to dcpofit its (alt, and congeal. E. 1- [As this hot air does not immediately quit the earth, I {houid conjefture that it is Jr} air, for vapour would feem to make it more buoyant, and carry it upward! from the furt‘ace. Accordingly thefe very winds are fuppofed to have become heated over dry fandy defarts; and though in fome cafes they pafs over a narrow fea, yet they do not immediately perhaps acquire much humidity; the air not always appearing to imbibe humidity from the {ea itfelf in the firfl inllauce, but chiefly fromthc vapour emitted by means of the {car's own preper heat, which heat 9"- [Dn ForRer was for three difl'erent warm feafons in or near the fimtlzzrn polar circle, and ohferved in one of theft: feafons {even dtfierent auroras in latitudes 580 and 60"; their appearance being much the fame as with us, [heating up from a dark {egment in the fouth. This number is but fmall; but he fays that he had ncver read or heard of any perfon who had before feemdiern. Indeed the navigators in tbofe parts have been few; and it is to be fuppoled chiefly during the fummer feafon. _ As to the auram auflrales, or fouthern lights, as they are called, teen m our own latitudes; They are hardly to be fuppofed to have marked bllbfl' frailr (lied/42:11]")! limit/11mm; {ince our own northern lights are only now and then 0 down as in the Mediterranean countries. erve dad 0;" The {uppofittun alfo 15 too biparhe , .0 [try that they are formed over infulating dry ground to the fouthward. b t ere tll no millake therefore in the relation of them, they maybe guefied t? e owiizgth: d: electric matter propagated along the yacuum, but originating 1:5 to 1:5 oudrclei; -u go ayc north; that origin however being Either faint, or havmg ta en 1) ace mEa] y g light, or under the fcreen of clouds.--(SEE Dr. Forfler s Ohfervagtogns round the world, I). no, and the Philof. Tranf. for 1764., p. 32 - .) . as very inferior to that of the winds in quefiion. L] ' the Uuu [15‘7- |
