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When ain-Water is oured doWn pono par of the sursace sine ea, in squilibrium emeen that pari and the surroundin ocean is in tho firs instant disturbo domno in bottom; theno a loW, generalmotion of tho ea-Water Aes place, bereb the leve os in surrou diu wator is lighil ratae and that os the ianwate stratum lowered. But tho inhin os the fres Wator cannot hoWeVer proceed sarther, thanto bout tho oin determine by the specific gravities os hos and saltwater Another motion is thereis caused namel a superficiat current, flowingout rom theores mater-stratum in consequenc os the dissereno os pressure in the nuperficia strata. hould the ain coase, resulta illensu precisel analogous to those, hic tali place etwein a armor superficia stratum and the surroundin colde Wator But holit thorain continuo illi unabate pomer, the stratum os res Water must continue t enoreas in thichneas, untili in consequent is os levo is sussicient to mahe a sursace-current, that carries ossis much Water in annit os imo a tho ain felds. In his asscit seem to e evident, stat, in rogar onj to the differetice of pressure, ut a superficiat stream hould e produce Without an under-circulation. Τhe superficiat currenis, arisinis rom meteorological Wet, frequently have a reat velocity, since tho p. gravities os res mater and ea mater are ver different; at 15 C. the relation is as 1 1.027, and ati C. M 1: 1.0283, is the ea-Water contians V, p. c. sali, heroas in greatest differeno os Ap. gr. that in the ocean an aris hom disserenoesis temperature, is bout aso: 1. 43. O the ther han it is asib osti that, is Warmin in the ne case an res in the ther caused quia difforoticoso pressure at in heavior ater sursace-stratum, the 6pth, at hichequilibrium prevatis, must in generat e greater in the sorme cas inani in latior or, in ther ords, the superficia currenis caused by rain, flo in a shalloweris than hos caused by heat, provide in maximum os difforenco os pressure is equia. But then in disserenoes os prossum ars malle at the subsursace-strata os the hallower stream than at thocorrespondin strata os the deeper, and the forme ought thus to movoles rapidi than the latior. h intermixtur os sal Water hom bolowwillis courso influenco the motion to that question Pshali retur sarther n. Τho iantat at ea, is ascis no , very nequali distributed,
tho groatos abundanos fallincto in tot os ins hios latitudes, parily
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12 F. L. ΕΚΜΑΝ, in tho Orm os res an parti in that os melliniice, an another notinconsiderable quantit salsing on a narro bel in tho vicinit os insequator tho tW intermediate oves, hom nea tho quator o bouf
nora result sciat a se then, separatet considered, ought o bo oursuriac current debouching po the gones ii supplied Wit rain: twogmater, car in col and tae se Water rom the oles to tho tr pica, oriatin toWard the autem, and Wo maller homine quatorto in tropics, deviatin toWard the estem comis. An other an by O means inconsiderable amount os iantali is carrie into in se by the rivera tho mouina os,hic formius commencementa os currenis, hic howeve usuali hau oes a loca importance. In an places, . . in in Shagerach, here in colloctedmaas os severa rivors salis in at ne and the fame creeh, in quintityos reali maior an neveriheles bo sufficient to ive riae to stream ofauch trono an extent, that the mustis attende to in navigatio an ove in the question os in generat oceani circulation in influenco, Whic ino utpourino os in rivers may exertis the water motionmuat no bo entiret lest ut os consideration.
In hos Water evaporatio cauae a sinhing os in auriaco an acoolin os in externa atratum. When se mater Vaporat , ita salinissala also enhance an accordingi ita specific eight increaas homowo causes, producing, a MUR has Hready hom, a Vertica circulationwithin the vaporatin locality. his vertica circulatio however oonroachos a limit, beneat whicli it cannot eauit extend. In hos regionaos in ocean, here evaporation is greatest, in sola heat operates montpoworsutly thus in increaain os in specific gravit is counteractod by the eat, and by ther reasons, strata, stat are eara in cons quonce of lower temperature, eo there constanti rising to tho sursaco Agat in localitios, horo in auriac dial lose more hea than it ceivea, the vaporation is lituo compare Wit tho accensiona os hostimator, an in alisin auriace-Water heresore oon moes Wit atrata
os sussicioni salios and woight to rende in circulation dissiculi. Os much greator importanc in the oceani circulation is hochange os love produco is vaporation sor in increaae hydrostatio pressure, arising hom in increme specific eight in vanishingi amass
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in comparison it the decrease, produco by the diminutio os inomate viar' height. No an vaporation ahes placo illi ver different rapidit in dissoroni localitios an attain iis maximum in tho regions, whors the iantali is east, vig the region os in trade--nds, his circumstance must necessarii haVe a considerable influenc on in oceaniccirculation.
By vaporation in equilibrium os the wator-particis is disturboddown to the ouom, an accordingi in motion, hic t es place in ordor o filiis the vacuum ma extendo the wholo mass, althoughtho volocit mill o diffsron a disserent depilis. Is, suppos a cup- sh ed hollo in o sormed is vaporation in the ursace of a mas os mater, the disserenos os pressure in th levet, that passes throno inscontro os in hollow, ill bo greator than in an leve above it, and thomotion os the water-particis in that plane in there re e mors rapidina in an plane bove it But in ali lows levet in difforonos os pressuro is the samo as in that levet, an it ould consequently be un- remonable o suppos that in hollo Would e fille onlymis superficialatroam os ita oWn opth. otion mus alno aris in the lower strata, and this motion undo tho contro os in hollom mustae Vorticali upWard. It wil accordingi dependispo the relative dimensions os the watermas and the ollom, an on in inclinations os the latior's ursace, whothor in fissin os the ollo bo Win mors to tho mucos thewator hom in fides o the ris os that bonoath. Τho spression os in ocean's ursace throtio vaporation is extromoly mali in comparison to the extent os the sunken ursace, and tho volum os in hollo is extremel smal in comparison it that os in ocean. ho motion heresere os in approachin particles unde thos saco os in hollo mill e chiefly upWard, but Will graduali approachio horizontal, a the distanc homine localit os in hollo incremos. Τhns in great vaporatio Mihi in torridisone uot o produce twoslow, se motion in the ea, ne in acti hemisphere, hich, originatin in tho hios latitudes, meet in the nolo urhood os in equator. Α evaporation is greater in the regions ea in equator than in thoso more distant cis Wo excepi in narro squaloria bol that includos the region os the iam an rain, in quantit os mater, hic in auia os timo must floW to the sorme region, Willi relativel greator inanthat, hic moves toWard the larier; ut in forme must pas inrouo
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14 F. L. ΕΚΜΑΝ, move it a reater Velocit toWard the lower latitudes, than towatas the paris os the vaporatin regio more distant froin the equator. do not know that attention has been pia to the importanc ofovaporatio sor the formation os the old under-current in the ocean ), Wherea evaporatio has long been recognige a the cause of the u renis that exist etWeen the ocean an separate basin suo a in Moditerraneati, in hicli the annuat vaporation Oxceed the iantali. vetiis vaporation in Euch a basin mere o more rapi than in the eigh- bourin portions os the ocean the leve os the basi mus neverthelefasin relati vel to the ocean's, ecauso the contractio os in basin's
molith in a certain degre obstruct in under-circulation, hich in theocea carries ater hom localities os vorabundant ainsal to thos ofoverabundant evaporation. ΑΗ regard the natur os the stream, produce by evaporation, hen paRSin a relativel narro canat, suo asino traiis os Gibraltar, it must necessarii bo ver different hom thostream, hic evaporation causes in the ope Ocean sor in proportionbe eo the vaporatin sursace and the area os in sectio of thostream is in his case altogether different. Should tho sectio of tho cana in proportion to the quantit os mater, that must pas throuo itin a uni os time in orde to compensat the vaporation, e les thau a certain limit, there an e ni one stream, hic Williso in tho evaporatin region, here the salines in Such casos must continuassyinoroas Whon tho dept of the sectio is greator, here vin thet In his explanation have ahen account os nomine cause than Vaporation, nor of the circumstance, that by evaporatio the salicis test in the mater, hereb thecurrent might in time e considerabi modified even is exclusivel arising romevaporation shal have occasio further no retum to this question. Wo do no a present know os an suo case; ut stat unde pastineologica period basin have been graduali so ut miro communication it theopen ea, that an effective doubie circulation ecam impossibio, is evidenoed by the numerous deposito layer os ordinar sali, more or les visibi accompanie by theringrodient os oceani sali, as also by the pure sulphur in certain sedimentar formations probabi originating in ea-Water sulphates after thei reductio throuo organi media The proces os these evaporating-operations has probably been that hontho ut ard under-current, in consequence of the increasing hallomnes of the mouis,ceased the content of the basin have by the continue stream os sal mater Domtho se been converte into a sal lahe, hic eventuali christaliged. I has thendoponde on other circumstances, . . the muco rive mater, hether the residuallyo has been carriet ossi ros in the formation os the Stasssurier-strata, it has riedup. The ne proposal to convert the ahara-desert into aciniand-se Would doubilesstea trio a simila result.
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sorm a closed hirl-pool. Loca circumstancea must determino, Wic os these motions the under-current o the latera eddies, orna tho Heschannet, hereb tho artificiat ator carrie os by tho in find iis Way bach. In ahes, here in consequenc os their mali extent tho indcover almos the whol auriace, the vertica circulation, hic is o in- dispensabio a condition sor the hoshnes os the water, is in a very great measure maintaine by the wind ). In the ocean o the contra , tho ursaco os hicli an only bo partiali covered by an particular Wind the superficia stream produce must also e accompanted by side-oddios Tho dissorenco os lovel e ee two opposite coasis, hic a win os great extent an here cauΗe may in consequenc os the great longili os the surtace, on hic tho in acis, e considerable eventhough tho foro os tho in bo ut moderate: ho vast tho difforencosos lovet, hicli violent indu an produco, is ussicienti evidelice bytho o-calle storm-floods That the trade-windu Whicli collec the waterto ard the equator hom . . and . . and rivo it toward thoeast, are the QSe of the so-calle equatoria currenis, is no perhapadoubio by obo . t eam also cloar that an elevation os levet, caused by theso indu on the easter coast of the continenta, has amatoria offoc in tho formation os tho Gulnstream, and that this in con-jnnution illi a correspoudin sint in o the wester coasis causes thewhirlin motions illi argasso in thei contre, hicli in the norinem hemisphere in consequence of the forin os the continent are o clearlydoveloped.
V:, Stream caused by the mechanica essees of a mas of mater,already in molion, n he elyhbouris parficies of mafer:
Tho sollowing oxamplo Do the ah Arstauthen atratockholm here deservos perhapso be noticed. he alie has an arro communication illi the Malarens, the wator of Whicli contains a lique ait A longos Arsiauthen is Dogen the deeperisator also there is ound to e lighil salter. e. g. 0.o p. m. chlomatrium at thesursaco, 0.08 at V sat hom depth. ut a soon a the ice is melle and the windcanoreel operate on the sursace the salines of al depilis is uniform and continuos o at the summer The undulation in that litile ahe is os courso ver inconsiderable so that no ther cause an e assigne so the ac mentioned then the genera circulation caused by tho inds.
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propagate to the localitios tha that, here the orcss, that originalty produce it, operate. But a stream a throughout iis hol courso bymochanica action ive is to secondar motion in the surroundingWator, an it is to stream os his hin that o halliso foris hilo
Whereve a stream floWs in contac With a quietis more quiescentinas os Water, the molecule os the forme Will by frictio communicato par os thei motion to thos of the lauer. he quantityi tho floWingwator is thus increased, Whilo the volocit is diminishod. Without at firs occupying oui selves it the question, in hat relatio the veloci
os lis thus increasta stream standa tociis mass, e ma noverihelesSconcludo that a diminutio of the mas in the surrounding Water must talio Place at Ver Spol, here the stream communicate iis motion to the
particles of that ater, an carries them WV in iis own diroction. his diminution, liho that caused by evaporation o by iud, muSt produce achange of levet, herob the equilibrium is disturbe doWn to tho bouom, and this disturbano again must produce an assiux os ater to the placein question, hereb the ater carrie ost is replacod. he sat diminution anno evidently be compensated by the origina stream itself, sorthis ould requiro an increas of the stream Velocity in conSeqnencewhereos the quantit os Waler-particles, carrie os by the stream, ould Oven e increased or in ther ords, the levet ould e continuallysinhing in tho par of the stream bellin that, here the ne moleculesare et in motion. o suppos again that the old an o filio u byno molecules of the increased trem, ould e evidenti tantamomitto supposing that the motion, hich ad cause in void, ha no talion placo. O tho ther an an assio rom tho more quiescent Water, ut-sido the stream itself, both an and must tali placo, hicli motion illbo simila to that generali brought abola by the disturbano to an un- limitod opth os hydrostatio quilibrium. Τho volocit of the increased stream is another potnt os importance so the question Is, designate illi Malis velocit an Wit m tho massos Water of the origina stream, hic passes by in a uni os time, and with v and M velocit an mas os a solioWin pari, horo it has tinenu into itaeis ne molecules, supposing the velocit to decreas in tho
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as mi tho other haud alio strosem' vis viva must e constant, is,eneglect the quantit thereos that by rictio is convorte into eat, 'e
ira mas incre es Henco the moloculos in tho solioWin par of the stream have a tendenc to separate thomsolve Dona hos in the pre- coeding, o in ther ordου the quantit os ater at tho locality e re considering suffers a decreme. Is the stream e a superficiat ne, thelove os in morin Water hould bo thus loWered, and is an under- current, in leve of the wator abovo hould also e lowored. he hydrostati pressure os the movin Water-strata is then reducod, and in consequenc thereos an muco water hom illo surroundingistrata Ehouldio place in direction to tho somor. The mucos mater, required sorthe replacement os molecules carris os by the stroam, is thon holped by tho taci, that the velocit of the thus increaso curroni oes no de-oreas in the proportio os tho increas of the mass. In ordo in future t have a hori nam so the motioris, hicha stream thus produces in the surround in Water, I avo denominated these motion reaction-strea=ns It is asil seen that streanas of this End, hicli in particula circumstances may be harpi define and quite poWersul, mu8 Ver frequently aris in the ocean. he must in the firs place accompany such treanis, a originate in a disturbarice of thoequilibrium, extending oni to a certain depth, hethor the disturbingcauso b heat or ain, o both united. ut also the superficia streams, caused by the Wind, and the under-currenis, produced by the heavior ator' sinkin and dissusing itfel a the ocean's ottom, mustinive riset reaction-currents. he velocit of thes stream ought chioflyrio dependo that os the origina current and tho area os the section, in hicli thostream, arising rom reaction, has to move. hat area is osten e great an in reaction-stream consequently carcet senSibi a n Separate stream. he stream caused by a disturbano os equilibrium, extendin doWn to tho bottom ought to solis least calculate to invoris to reaction-streanis in aci, in these cases, tho origina motioniiset tinos placo in ali strata, though With distorent volocit a disseront depilis, an iis velocit is moreoVer usually mali.
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aris fro many causes, I Wil hero in the firs place confino, si tothos produce by the outflo os rivors, ecause hom the specia examplos os such streains, hicho hau the opportunit os adducing theroador ill e bellor abis to forma iden os the natur os reaction-
It has long been observo that in stratis, hic unite the oceanwith separate oceani basins, in hic the annua influx of river ater exceed the vaporation rom in sursace there is beneat the superficia current, hic carries os the superfluou river-Water to the ea, an under-current os sal mater in the opposite direction. his phoenomenonis in ac os a stili more genera naturΘ. very rive or brook Whichsalis into the ea, givos ris to an under-current directe toward iis embouchure. hes under-current are so distinc an in causea, that produce them, o active, that in calm easter inela presenco a beeasit observe at the mouin os tho mos insignificant rivulsi, that talis out ver the ursace of the ea. Ι has eo usual to explain the under-current in such traitS, Se g. refund is supposing that the ea-Water ouiside in consequenceos it greater specific gravit displace th laesher and toto mater in the separate ocean-basin and thus flows into it in tho formos an
facto . Is e supposed the outflo homo river suddent to stop, as Oon a tho rive had deposito a certain quantit os res Wator onthe sursace os the ea, o only ould assuredi a superficia current oso flowin hosti ater ariso, ut also an under-current os salt-Water in the opposite direction in consequenco os in Wato stratas differences os pressuro, and thes Would continuo tili in hos mater a carris oss accordin to hat has bovo been explaino mors fuit in in cauo offusam caused by hoat an raintail. ut is in rivor continue t fio mit the samo velocity, hic causod in formation os the fresh-Water- stratum e re the mouth, it eom cloar, that ater could notisun aWayin consequenc os in exces of hydrostati pressure more rapidly than
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20 F. L. ΕΚΜΑΝ, that the rive Water, streamin onWard rom ehind, could constantly supply the oss, caused by the outflow, an preserve in leve unch-ged. hus tho cause of the under-current, hicli in the forme casema occasione by the reduce hydrostati pressure os the superficiat mater in consequonc os the inhin os the levol, oes no in his caseexist Hono the dissereno os spe is Wotot emeen river-- se Water ouo hore ni to produce disseretices os levet, hich also houldbe constant a longos in suppi os rivor-water is continue an constant. I look po the under-current, hich, in these cases, ery distincti appears, as a reaction-stream, to e accounte sor o the genera principies, bove lai down so tho explanation os suo utroams. ut the fame causes, hic produce an unde current at the moutha Privers, must also ive is to an under-current in the channeis, hereb separate ocean-basin discharge thei superfluous restier ater into the ocean. Τhis sosm to b the place to a a se morda on the reaction-stream in ahes a compare Wit thos in tho ocean Our nowledgeos tho Ormor is indeo ver scatityoneVeriheles the generat Xperiencemo have os troam in ahes ould sesin tociustis our assuming that the under-currenis, produce by the reactio os rivera in lahes, ars sarinferior in intensit to thpse produced in the ea. What then, it illbe Ahod is the aus os this difforenco, is the under-current in the ea is no caused by disseronce of pressuro depending on the different specific eight of tho Mery In the firs placo the batiges os levet, occasione by the ouringos res mater into resti, an oni produce suo disturbancos os equilibrium a extendisti the way to the bottona; ut the movemenis that resul hom his disturbances, ovo not a I have jus Haid, o bo solio-