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Show 94 'VI N D S. NoTE XXXIII. the whole atmofphere. From the journals kept by the Royal Society at london it appears feldom to 1·ary more t!LJ.n two inche!", or one-fifteenth of the ·whole a:mo fph er~ . The qua ntity of the va riation is faid f1ill to deer afe neat:er the l111e, and t_o tn crca fe ~n the more northern btitudes; which much confi rms the tdca that there cxtfl:s at certam times a areat defl:ruEI:ion or production of air within the polar ci rc le. July;, 1732. The -wel1aly winds in the journal in the Medical Effays, .Vol. II. above referred to, are freque ntly mazkecl with the number three to fhew thetr greater velocity, whereas the eaf1erly winds feldom approach to the number two. The grc:lter velocity of the weiterly winds than the eafterly ones is well knowu I believe in ev ry climate of the world; which tmy he tl11ts explained from the theory above ddi ve red. I. When the air is f1ill, the higha parts of the atmofphcre move q11icker than thofe p:uts which touch the earth , becaufe they :ue at a gre:lter difl:Jnce fJ~t. m tiK a)>.is of motion. 2. The part of the atmofpherc where the north or Iou th 1' 1 td comes f1om is higher than .the part of it where it comes to, hence the more elt.v:AtLtl parts of the atmofphere continue to defcen ci towards the earth as either of t!nC.! wi nd~ :.ppr l:lCh . 3· When fouthern air is brought to us it poilc..-flcs, a wcfterly diret ion alfo, owiug to the velocity it has previoufly acq1t ired from the earth's fu rface ; ami if it conJ:!, ~ of :Air from the higher parts of the atmofphere defcending nearer the earth, thi' W t Herly velocity becomes increafed. But when northern ai r is brought to us, it pofl-:..l!i san apparent eal1erly diretl:ion alfo, owing to the velocity which it has prcvioufly acgu ircd from the earth's furface being lefs than that of the earth's furfacc iu this lat itu rlc; now if the north-eafl: wind conll fl:s of air defcending from higher p :~ rts of the :::tmofphere, this deficiency of velocity will be lefs, in coufequencc of the Came caufe, viz. The higher parts of the atmofphere defcending, as the wind appro:Khes, increafcs the real veloci ty of the wef!:ern winds, and decrcafes the apparent veloc ity of the caHcrn ones. Oaober 22. Wind changed from fouth- eafl: to fouth- wef1. Thct e is a popular prognof1ication that if the wind changes from the north towards the fo 1th paiii11g through the eaf1, it is more likely to continue in the fouth, than if it paffes through the wdl, which may be thus accounted for. If the north-eaf1 wind changes to a north-wefl: wind, it fl1ews either that a part of the northern air defcends upon us in a fpiral eddy, or that a fuperior current of fouthern air is driven back ; but if a north-call wind be changed into a fouth-eafl: wind it O~ews that the northern air is become retrograde, and that in a day or two, as foon as that part of it has palfed, which has not gained the velocity of the earth's furface in this latitude, it will become a fouth wind for a few hours, and then a fouth-wef1 wind. The writer of this imperfect fket ch of anemology willies it may incite fome perfon of greater leizure and ability to attend to this fubjeCl:, and by comparing the various meteorological journals and obfervations already publifhcd, to conf1ruCl: a more accu. rate and methodical treatife on this interef1ing branch of philofophy. 95 NOTE XXXIV.-V£GETABLE PERSPIRATION. And 'Wed the enamoured Ox)'gene 10 Light. C . . ANTO IV. l. 34· WHEN potnts or hatrs are put into fipring w t . h - a er, as In t e expe . f s· Thompfon, (Philof. Tranf. LXXVII ) nnd r d . rtments o tr B. . . . cxpote to the ltght of th fi h atr, whtch loofcly adhered to the water rifes · b bbl . . e on, muc F V . ' tn u es, as explawed m the t ucus, ol. I I. A fltll greater quantity of air and f k' . . no eon P · fll ' ' 0 nen ey s green matter, and by vegetable leaves a· pur.e r tnd, .t s emttted bY D1. ' . ' growmg m water m fun-!hine a cordtng to Mr. Ingcnhouz s experiments · bath wh' -I I fi r n . ' c- (j . f . , tel utpe'-L to be owmg toad compo tt10n o the water pcrfptred by the plant fo th d f . e- . . ' r e e ge o a c:~ptllary tube of reat tenu zty may be confidcrcd as a ctrcle of points and h . . g . I . . ' as t e oxygene, or prtnctple of vtta ::ur, mny be expanded tnto a gas by the fun's light h h d . . . . ' t e Y rogene or mflammable ;m may be detatned tn the pores of the vegetable. H ence plants growing in the 01ade are white, and become green b b · ft d the fun 's light; for their natural colour being bl th .Jd' . y emg expo e to . ue, e au tttOn of hydrogene adds yellow to thts blue, and tans them green. I fupp ofe a {j ·1 · fl • . 1 . . . 1m1 ar ctrcumnance takes place w anzma bod tes; thetr perfptrable matter as it efcapes in th r {] · b . . e tun- line ecomes decom-pofed by the edges of th etr pores as tn vegetables thou crh i 1 [: · h · r . . . I r ' o n e s quanttty, as t etr per- JptratJOn IS CJS. , .a nd by the hyclrogene being retained th e fk'm b ecomes tanned yellow. ln proof of .t illS It muf1 be obferved that both vegetable ancl an1'mal 1ru b(nl ances be come bl eached whtte by the. fun-beams when they are dead , as cabbage -ft a lk s, bo nes, t·v ory, tall?w, bees-wax , ltne~ and cotton cloth; and heuce I fuppofe the copper-coloured ?at.vcs ~f funny co untnes rmght become etiobtcd or blanched by being kept from their 1nfan~y 111 the dark, or removed for a few generations to more northerly climates. It IS probable thnt on a funny morniug much pure air becomes feparated from the d.e~~ by .means Of th P. po.ints of Vegct:~blcs 0 11 VI hich it adheres, and much inflammable a1r tmbtbed by the veget:Jblc, or combined with it; and by the fun's light thus decompofing water the effdl:s of it in bleaching linen feems to drpend (as defcribed in Note X.) : the water is decom pofed by the light at the ends or points of the cotton or thread, and the vital air unites with the rhlogiflic or coloming matters of the cloth, an l produces a new acid, which is cithu itf'elf colourlefs or m:dltcs out, at the fame time the inflnmmnble part of the water cfcapes. Hence there feems a re:~fon why cotto11 bleacl es fo much fooner than linen, viz. becaufe its fibres are three or four times fhorter, and th erefore protrude fo many more points, which feem to facilitate the liberation of the vital air from the inflammable part of the water. Bee's wax becomes bleached by expofure to the fun and dews in a flmilar manner as ml!tals become calcined or ruf1y, viz. by the water on their furfacc being decompofed; and hence the inflammab le matcri :d which cauletl the colour becomes united with vital. ~ir forming a new acid, and is wafhed a w:.~y • |