Meteorology of the Red Sea and Cape Guardafui Author(s): R. Strachey Source: Proceedings of the Royal Geographical Society and Monthly Record of Geography, New Monthly Series, Vol. 10, No. 11 (Nov., 1888), pp. 704-708 Published by: Wiley on behalf of The Royal Geographical Society (with the Institute of British Geographers) Stable URL: http://www.jstor.org/stable/1801400 . Accessed: 20/06/2014 14:33
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This content downloaded from 188.72.126.108 on Fri, 20 Jun 2014 14:33:13 PM All use subject to JSTOR Terms and Conditions 704 METEOROLOGYOF THE RED SEA AND CAPE GUARDAFUI.
To the west dwell?or dwelt?the Abchasians and Cherkess (the Circassians of romance), tribes of whose origin, affinities,and customs we have still no fully satisfactory account. Recent enquiries pursued among Circassian exiles in Turkey have led a German investigator to the belief that the leading families at least had connections with Arabia.* " iEschylus, we may remember, wrote of the martial bloom of Arabia, who hold a citadel on lofty crags hard by Caucasus.,, Are the Cir? cassians Semites ? What is their language ? Much remains to be done in investigating the antiquities and origins of these loose confederacies of chivalrous but semi-barbarous tribes, and in clearing up their historical connection with their neighbours on the north, the Tartars of Karatchai and Uruspieh, and the tribes of the Kabardah, who apparently came east- wards from the Crimea.f It is time that I brought to an end this discursive?some may call it, not unjustly, desultory?paper. I shall submit cheerfully to the criticism, if by touching on very various topics I have, perchance, attained my object, to show that it is not only to mountaineers and geographers that this great mountain country is interesting. The Caucasus ought for many years to come to provide ample material for workers in every branch of natural science, as well as for historical and ethnological students; and, last but not least, for the lover of noble scenery and primitive life who views the out ward shows of the world without com- " mitting himself to the special study of any particular branch" of knowledge,? " Contentedif he mayenjoy The thingswhich others understand."
Meteorology ofthe Eed Sea and Ga^e Guardafui.% By General B. Stkachey r.e., f.r.s., pbesident b.g.s. Charts, p. 748. Weather Charts of the Bed Sea for January and July.?In these charts,which have been prepared in the Marine Branch of the Meteorological Office,under the supervision of Captain Toynbee and Lieutenant Baillie, the usual system of exhibiting the pressureand temperature,by isobars and isotherms,has not been adopted, as the necessary informationis entirelywanting. The diagrams, * * Petermann'sMitteilungen,' vol. xxxiv. * t For furtherinformation on Caucasian ethnology,see au * Klaproth, Voyage Caucase'; Journalof the Eoyal Asiatic Society,'articles by Mr. E. N, Cust (with list of authorities)and Mr. D. Morgan,vols. xvii, xviii.; 'Petermann's Mitteilungen/ ' vol. xxiii.; V. Miiller's Ossete Studies'; Prof. Kovalevsky's,Uslar's, and Schiefner's works(in Russian); E. Chantre'sfinely illustrated volumes. The above referencesare incomplete,but they may suffice to set a studenton the track. A fineethnological map of the Caucasus has been publishedby the Government. X Read to the GeographicalSection of the BritishAssociation, Bath, Sept. 6th,1888.
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therefore,have been preparedso as to give what may he terrneda sectionalview of the data reeorded,referred to a line supposed to be drawn along the axis of the Red Sea, correspondingto the usual tracks of vessels, and prolongedin like manner throughthe Gulf of Aden. January. North-eastMonsoon Season. Wind.?The northerlywind blows almost uninterruptedlyfrom the Gulf of Suez to about 23? N., and continuesas the prevailingwind to about 19? N., whilst furtherto the southwardthe south-easterly wind prevails. From 23? N. to about 15? N. thereis a minglingof the winds from the principal directionsof north and south-east,and from18? to 20? N. the winds fromthese directionsare of almost equal frequency(this area is shaded darker in the diagram). In the Gulf of Aden the wind is principally easterly, and draws somewhatfrom the northwardin the easternpart. Calms are most frequentbetween Aden and 20? N., hut they forma very small proportionof the observations. The forceof the wind is rather strongerwith the south-easterlywinds than with the northerly,and the strengthof a moderate or freshgale is frequentlymet with betweenPerim and 20? N. * Barometer.?The mean heightof the barometerranges from about 30 10 inches in the Gulf of Suez to 29*97 inches in about 15? N., giving a gradient of 0*13 in about 1100 miles. A second maximum about 30'06 inches is shown in the eastern part of the Gulf of Aden, givinga gradientof a rathersmaller amount,but extend- ing over only about half the distanceor less. The resultsdeduced fromthe several sources(logs in the MeteorologicalOffice, of P. and O. ships,and fromthe Admiralty) agree well among themselves. Air Temperature.?The mean air temperatureranges from about 64? in the Gulf of Suez to 79? in 16? N. In the Gulf of Aden the mean temperatureis generallyabout 77?. Current.?The general driftof the currentis to the westward in the Gulf of Aden and to the N.N.W. in the Red Sea; its strengthis very light, and nowhere does it exceed a knot an hour; as a rule it is less than half a knot an hour. Sea Temperature.?The mean sea temperatureranges from 65? in the Gulf of Suez to 79? in 19? N., and fromthis position southward,as well as in the Gulf of Aden, the temperatureis between 77? and 79?. These temperaturesare somewhat higher?1? or 2??than those of the air. ? SpecificGravity.?The mean specificgravity ranges from1 0314 in the Gulf of Suez to 1*0270 iu the Gulf of Aden, the decreasebeing fairlygradua1. July. South-west Monsoon Season. Wind.?The direction of the wind is generallyfrom the northwardand north-westwardover the whole area of the Red Sea, drawing more westerlyin the southernpart, whilst in the Gulf of Aden the prevailingdirection is westerlyand south-westerly. The mean forceof the wind is about the same in differentparts of the district,but the individual observations show that the forceof a gale is attaincd only in the Gulf of Suez and in the Gulf of Aden, strongestin the latter. Calms are about twice as numerousas in January and now formabout 15 per cent. of the total wind observations. * Barometer.?The mean barometerranges from29 79 inches in the Gulf of Suez to 29' 67 inches offAden, being throughoutabout 0* 30 inches lowerthan in January. The resultsobtained fromthe MeteorologicalOffice and P. and O. observationsare in good agreement. The gradient between the northernand southernends of the sea remainsabout the same, but the minimumin lat. 15? N. is no longerobserved, and with it the relativelyhigh pressureover the Gulf of Aden also disappears. Air Temperature.?The mean air temperatureranges from about 82? in the Gulf of Suez to 90? in the southernpart of the Red Sea. A sharp fall is shown on approachingPerim, and a second minimum of 84? is reached off Aden. These
This content downloaded from 188.72.126.108 on Fri, 20 Jun 2014 14:33:13 PM All use subject to JSTOR Terms and Conditions 706 METEOROLOGYOF THE RED SEA AND CAPE GUARDAFUI. temperaturesare higherthan thoseof Januaryby 18? forSuez, 11? forthe southern part of the sea, and 7? forthe Gulf of Aden. Current.?The currentis excessivelyslight in the Red Sea. A tendencyto a south-south-easterlyset is, however,indicated between 17? and 20? N., and thereis also some evidenceof a very weak northerlyset in the northernpart of the district. On approachingPerim there is an indicationof a currentsetting from the Red Sea throughthe straitsof Bab-el-Mandeb. In the Gulf of Aden a strongeasterly eurrent is manifestedon the Arabian side, and a somewhat weaker currentis shown to be settingto the westwardon the Africanside. Sea Temperature.?The temperatureof the sea ranges from77? in the Gulf of Suez to 89? in the southernpart of the Red Sea, and like the air temperatureit tben decreases rapidlyto 84? near Perim, the minimumof 81? being reached offAden; in the easternpart of the gulf it again increasesto 84?*5. These temperaturesare respectivelyhigher than those observed in January, by 12? at Suez, 10? in the southernparts of the sea, and from3? to 5? in the Gulf of Aden. The sea tempera? ture in July in the Gulf of Suez is 5? lower than that of the air, in the southern part of the sea about 1? lower. SpecificGravity.?The specificgravity ranges from1*0310 in the Gulf of Suez to 1*0267 offAden, whilst a slight increase is shown in the eastern part of the gulf. The winds and the currentsat the two seasons obviouslyfollow the pressureand temperature. The northerlywinds which predominatethroughout the year over the northernpart of the sea conformto the permanentlyhigher pressureover the Gulf of Suez. The southerlywinds of the winter in the southernpart of the sea * are at once seen to depend on the low pressure29 97 in about latitude 15? compared with the higherpressure 30*06 over the Gulf of Aden, where again in consequence easterlywinds prevail. The greaterstrength of the southerlywinds as comparedto the northerlyin January is attributableto the steeper gradient between the high pressurearea over the Gulf of Aden and the low pressureat latitude 15?, as com? pared to that betweenthe latterand the Gulf of Suez. The low pressureover the southernpart of the sea is evidentlyconnected with the permanentlyhigh temperatureover the same area. The northerlycurrents noted are very slight, and some introductionof water fromthe Indian Ocean is obviously necessary to replace the loss by evaporation which must be considerable. AlthoughI have not the precise figuresto referto, I may also mention that there is a perceptiblevariation in the level of the sea at various seasons, amountingit is said to a foot or two at least, dependenton the pre- vailing winds in the Gulf of Aden or Indian Ocean. This subject will require furtherexamination in connectionwith that of the tides at the two extremitiesof the sea. Sea Temperature, Currents,and Winds in the vicinity of Cape Guardafui during the South-westMonsoon months.?From a notice issued by the Hydrographer in 1882, it appears that duringthe six precedingyears seven vesselshad been wrecked and three stranded in the neighbourhoodof Cape Guardafui, and it was then considereddesirable to republishthe available informationbearing on the navigation of that locality. The wrecks spoken of, chiefly occurred during the period of the south-west monsoon?April to September. At this time vessels bound westwardthrough the Gulf of Aden usually approachCape Guardafuifrom the southward,passing between that Cape and the island of Socotra. The weather during this season in the neighbourhoodof the coast is usually stormy accompanied by a heavy sea, the currentsare strong,and the land frequentlyobscured by mist and haze.
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In such circumstancesit oftenbecomes difficultor impossible to ascertainthe ship's positionby astronomicalobservation, and all indications of the proximityof the land become useful. Special attention has thereforebeen directedto the con? ditions of the weather and sea in the vicinity, and the available informationis in course of compilation in the marine branch of the MeteorologicalOffice, the maps now shown being the resultsof the enquiryas far as it has yet been carried. The facts which the chartsexhibit have been more or less well known forsome time past, but it was very desirable that they should be verifiedas completelyas possible,and that errorsshould as far as possible be eliminatedand corrected,not only with a view to the practical value of accurate knowledge, but also to its bearingon the interestingphenomena of ocean temperatureand circulation. Sea Temperature.?The temperatureof the sea surfaceis seen to be much higher offCape Guardafui than off Ras Hafiin, during most of the south-westmonsoon months. In June, July, and August this featureis especiallymarked, the tempera? ture offCape Guardafui being generally80? or upwards,whilst offRas Hafun it is generallybelow 70?, and often fullyas low as 65?. The area of cold water along the Africancoast between Cape Guardafui and Eas Hafun is very obvious, though the want of observationsmakes it difficultto defineits exact limits. In June the isothermof 75? is seen to lie only 3 or 4 miles to the southwardof Cape Guardafui, and in August the isothermof 70? is not above 20 miles distant. In September, during which the south-westmonsoon is stili blowing, the conditions,however, become more uncertain,though the cold water is shown generallyto the southward, and the average temperatureis much lower offEas Hafiin than offCape Guardafui; on the otherhand, the thermometerranges high not farfrom Ras Hafun, and low at a very shortdistance fromCape Guardafui. In like mannerin May, when fora part of the monththe north-eastmonsoon often stili blows, and the south-westmonsoon if blowinghas not reached its full force,the water is fairlywarm over the whole area. The series of charts for the four months clearlyshows that as the south-west monsoonseason advances the differenceof temperaturebetween the northernand southernparts of the area becomes much more stronglymarked, the isothermsare closed, and theirdistribution more complicated. Wind. Birection.?The wind seemsto draw moresoutherly near Cape Guardafui than it does fartherto the southward,and on roundingthe Cape, and standinginto the Gulf of Aden, the directionis oftenfound to be south-easterly. Force.?The forceof the wind is very strong over the whole area south of Cape Guardafui embraced by the diagrams, in July and August,but in the other two months,June and September,strong winds are occasionallymet with. Sea or Swell.?The directionof the sea or swell is nearly always with the surface wind, and the observationsshow that to the south of Cape Guardafuithe sea often runs very high. Current.?The currentgenerally sets to the north-eastward;the observationsof this element are, however,too few and too scatteredto allow of any very satisfactory conclusionsbeing drawn as to changes of directionin differentparts of the area dealt with. The velocity of the currentranges fromabout 20 to 80 miles a day, and is strongerin July and August than it is in June or September. The daily rate is indicatedon the diagramson the shaftof the arrow. Weather.?Mist is veryprevalent in all the fourmonths from June to September, and it appears to be generalover the whole of the district. It would be prematureat present to offerany opinion whetherthe remarkably cold water met with near Ras Hafiin,is simplydue to the currentfrom the south,or
This content downloaded from 188.72.126.108 on Fri, 20 Jun 2014 14:33:13 PM All use subject to JSTOR Terms and Conditions 708 GEOGRAPHICALNOTES. whetherit may not in 'part at least be the result of the colderwater frombelow being broughtto the surfaceby the action of the south-westwinds, which during the summermonths blow so stronglyoff the east coast of Africa. The examination of the data forthe winter months, during which the north-eastmonsoon prevails, will assist, no doubt,in arrivingat a correctconclusion.
GEOGBAPHICAL NOTES.
British East Africa.?We call the attention of our readers to the " interesting paper on The Commercial Future of East Africa," by Sir Francis de Winton, read to the Geographical Section of the British Association at Bath, and given at p. 722 of the present number of the 4 Proceedings'; in which an account is given of the Imperial British East African Company, just instituted under a Boyal Charter, for the deve? lopment and administration of the British Protectorate in that region. News has arrived of the safe arrival at Mombasa, the chief port of the Company's territory, of the first party under Mr. G. S. Mackenzie, one of the Directors; and Lieutenant H. G. C. Swaine, r.e. (known for his official surveys in Somali-land) has been commissioned to explore the interior with the view, in the first place, of finding suitable stations. Great additions to our geographical knowledge may be expected from these pioneer explorations, and our Society has made a grant of instruments to Lieutenant Swaine to aid him in making the fullest use of his oppor- tunities. Dr. Hans Meyer's Second Expedition to Mount Kilima-njaro.-~In consequence of the disturbed state of the country on the East Coast and in the interior of East Africa, Dr. Meyer's new expedition to Kilima-njaro has been suddenly brought to a termination. The large caravan, which started from Zanzibar about the middle of August, was disbanded a month later in North Usambara.
The Mai Kassa, or Baxter Eiver, New Guinea.-?This river, which itself discharges into Torres Strait about 80 miles west of the Fly river, has been hitherto considered as belonging to the great delta region of the but a recent Fly; survey (in April and May last) by Mr. C. E. Strode Hall, under the orders of the Commissioner of British ISTew Guinea, has definitely ascertained that it constitutes a small and curious independent river system. Mr. Hall followed up in succession, to their sources, all the streams, fifteen in number, tributary to the two main channels of the river, and found that the furthest source was distant about 25 miles from the Fly. From the observations taken, he says it is proved that the distance up the river travelled by Captain Strachan, and also the size of the tributaries, were greatly overestimated by that gentleman. The on country the banks beyond the mangrove zone is low-lying, open
This content downloaded from 188.72.126.108 on Fri, 20 Jun 2014 14:33:13 PM All use subject to JSTOR Terms and Conditions RED SEA. JANUARY.N.E. MONSOON.
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aa-ftft3 *?*&?*?**rtfc?Jtoe? This content downloaded from 188.72.126.108 on Fri, 20 Jun 2014 14:33:13 PM All use subject to JSTOR Terms and Conditions SEA TEMPERATURE, CUR SOON. ON. UCMT ?? WIND FREftHm~* Pubh*h*&fvrlh+J+ocmdMrtg?ofM* RoyaL CtograptucoJL Soaefy 1888. This content downloaded from 188.72.126.108 on Fri, 20 Jun 2014 14:33:13 PM All use subject to JSTOR Terms and Conditions SEA TEMPERATURE, CURRENT, WIND ano WEATHER. OFF CAPt GUARDAFUI AND RAS HAFUN . 52- 63* 51* -52* UCMT ?? WIND FREftHm~* iphvutJLSoajty 1888. W?J*I>Mr.faA. *33rm?r .V*W This content downloaded from 188.72.126.108 on Fri, 20 Jun 2014 14:33:13 PM All use subject to JSTOR Terms and Conditions