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Show Height and denfity after Atmofphere. 514 By w/Jat Stages t/Je E/efirz'c Ffizz}! 7-er, {9"5, 51 5 on a cold portion ofeartli, where the fun could not melt their con- of [ f § i7. Dr. Franklin very early obfcrved that a (17:); cake tents back again; we might then expect a proportional diminution this was in ice, or an ificlc, would not conduit 21 ihock. But America: Our ice here is feldom f0 perfeftly frozen in our experi- ofour itiategs, and as far as that eaufe goes, a correfpondent addition to ‘ our am, as well as--but in a cafe of f eeul ation ‘ ‘~ ‘' 0111 ments. (See his Letters, 5th edit. p. 36,) E] time to flop. about by the [ I § 18.---" Snow upon frozen ground, driven Winthrop mentions a " wind, retains its electriciry."---l'rotcnor d atCamfingular .fat‘t ofthis kind to Dr, Franklin, "illCll happene air alleys he. bridge in New England, in latitude 42", where the 5 edit. p. 4+4, E,] came electrified. See Dr. Franklin's Letters, [ 1‘ § 20. --" eleé‘tricitv (Ir/(i'nd/ng with thatfuow."-Ifone may the reprefume to queition this wonderful man, lwould alk, Why dundant electricity lhould rife only from the fnow and hail that has hail "hilt: actually diy'cmdu/ ; and not from the fame {now and and forming in the air? Is not every thing fuppoled faturatcd, from that therefore repellent, below; and is not the diltance lhortcr the part of the air where the clouds are, to the vacuum, than from ice to the vacuum; and does not the tluidthus avoid "HM/J the denfefi, that and confequently inoft refifling portion (if all the air, namely, wiiich lies between the ice and the clouds? In then, why my we pollibly not leave room for every circumltauee to operate, that Can dileniiiiigle electricity from thefe bodies \\llilL‘ in the regions of the furair, indeed of confining ourfelves to what happens on the mere face of the earth? May not a cloud as nccellarily lighten up into (where the (oxidaflirlg vault-m: in thofe latitudes, for initanee, as here it has both ways to choofe) it generally prefers to lighten drum into the (ofldla‘iflg earl/I7 "' .9 t But perhaps it feeined to be doubted whether the cold is not at fome feaf'ins too great for the exillence x f clouds (or in other words. of uncondenfed vapours) in thefe latitudes; as it certainly feems to be tor the formation ofueep fpringsi-But if there be a latitude in which on account of the cold, tllL‘IC are at no Limt: clouds; in that latitude there can be at no times fn'iw or hail, (or even ice, uuiefs produced before the prefcnt .ii'rangcmeiit .xf the t‘artli ;) and confequently no electricity Cull (ilel'c he brought down, and no finchzii'ge of it exilt. And in fuch cafe there tvouli be a bound, be) untl which, hand, at mat feafon the aurora \""iild not writhing.» ()n :he other ihouhl the clouds be permitted in any quantity to empty tlieini‘elves to * [See the 4th quere in the note to article :S.-The only ohjeé‘ticn feems \h ll one be, that in the former cafe the «(lance may be too great {or a [lb-74w; f0 enuugh near get can it before another, lei/f firatum of fluid mull b: hCJpc] on i. : bat to the vacuum even fur a gradual diltharge. .E._] E.] P u IKE 36226;};225tigfiaglcén'tinufs {umpienély intenfe for infulatioii I ‘ -. -- appieacn that Dr. Franklin here 1‘ {tm' 1 (igitens its own theory , and that, at certain feafons at lead, and .llPOn land, it extends much further, even in the northern hemifphere. l‘or confirmation fee the note to § 18. E. " H [ § 22,-" Height of the‘atmofphere of the poles of {itch denfity' . as to ohfiruét the warm: ol the cleftric fluid, See." It is I be- lieve generally agreed that within certain diiiances from the earth, whatever rarity the air has at a certain height, at twice that height it is twice as rare, at three times the height four times as rare: The height going in an arithmetical, and the rarity in a geometiieal proportion, hand in hand. Thus if the air at the equator was found almoil twice as rare at three miles high as at the earth's furface there, we may poflibly fnppofe it entirely {0 at the pale : Then at the pole, the air at fix miles high will be four times as rare as at the furface, at nine miles eight times, at i2 miles 16 times, at 28 miles 600 times, and at 40 miles 10,000 times as rare.~ Our molt perfect air-pump, on the other hand, ratifies mere air only 600 times (though air 7211'er quit/2 vapour, it ratifies to or 20,000 times,) And it is fuliieiently known how eafily the electric fluid traverfes this and other valily lefs perfect vacuums ofart :-Whether more or left; rapidly, provided it be done at all, is of little confequenee to the theory: only it is to be conjectured, that the higher the fluid reaches, the eafier becomes its paffage, at lealt under certain limitations-«As to the flooring of the fluid along the vacuum, as {con as arrived there ; it is a (uhfequent and totally dilliuit operation. But perhaps the above meafure is exaggerated for the pole, And, though it is not fafe to go minutely into the queliiun, yet the atmofphere itfclf, feenis ulually thought too far extended upwards; as the very grit-vii} of the particles of air for inftanee towards the earth (which is a body {0 large and mafl'y,) may he l‘uppofeil power- ful enough to orerbalan e their rcpulfion to each other when they aé‘t at fu'ch vaii diliances, and from fuch point: of repulfive matter onlv, as fuch rarity implies. When the aurora is fluted by fome, to have rifcn to the human/E bright ofhundreds of miles, becaufe then through an iinmcnie ex- tent ofcountry ; fuch coaclufion ought to be made from particular mar/int which the phienomenon has afforded, for tracing and identiillufying it through different regions; For as to a mere confufcd U u u z 01‘: y, u h mutation |