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ENGLISH CHANNEL (commonly called " Th...
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See also:ENGLISH CHANNEL (commonly called " The Channel "; Fr. La See also:Manche, " the See also:sleeve ") , the narrow See also:sea separating See also:England from See also:France. If its entrance be taken to See also:lie between See also:Ushant and the Scilly Isles, its extreme breadth (between those points) is about too m., and its length about 350. At the Strait of See also:Dover, its breadth decreases to 20 M. Along both coasts of the Channel, cliffs and See also:lowland alternate, and the See also:geological See also:affinities between successive opposite stretches are well marked, as between the Devonian and granitic rocks of See also:Cornwall and See also:Brittany, the See also:Jurassic of See also:Portland and See also:Calvados, and the Cretaceous of the Pays de Caux and the Isle of See also:Wight and the See also:Sussex See also:coast, as well as either See also:shore of the Strait of Dover. The English Channel is of comparatively See also:recent geological formation. The See also:land-See also:con-nexion between England and the See also:continent was not finally severed until the latter See also:part of the See also:Pleistocene See also:period. The Channel covers what was previously a wide valley, and may be described now as a headless gulf. The See also:action of waves and currents, both destructive and constructive, is well seen at many points; thus See also:Shakespeare Cliff at Dover is said to have been cut back more than a mile during the See also:Christian era, and the cliffs of Grisnez have similarly receded. Of the opposite See also:process notable examples are the See also:building of the pebbly beaches of Chesil See also:Bank and near See also:Treguier in See also:Cotes du See also:Nord, and the promontory of See also:Dungeness. The See also:total drainage See also:area of the English See also:rivers flowing into the Channel is about 8000 sq. m.; of the See also:French rivers, including as they do the See also:Seine, it is about 41,000 sq. m. From the Strait of Dover the bottom slopes fairly regularly down to the western entrance of the Channel, the See also:average depths ranging from 20 to 30 fathoms in the Strait to 6o fathoms at the entrance. An exception to this See also:condition, however, is found in See also:Hurd's Deep, a narrow depression about 70 M. See also:long, lying See also:north and north-See also:west of the Channel Islands, and at its nearest point to them only 5 M. distant from their outlying rocks, the Casquets. Towards its eastern end Hurd's Deep has an extreme See also:depth of 94 fathoms, and in it are found steeper slopes from shoal to deep See also:water than elsewhere within the Channel. Nearing the entrance to the Channel from the See also:Atlantic, the 100 fathoms See also:line may be taken to See also:mark the edge of soundings. Beyond this depth the bottom falls away rapidly. The See also:loo fathoms line is laid down about 18o m. W. to 12o m. S.W. of the Scilly Isles, and 8o m. W. of Ushant. Within it there are considerable irregularities of the bottom; thus a See also:succession of narrow ridges See also:running N.E. and S.W. occurs west of the Scillies, while only 4 M. N.W. of Ushant there is a small depression in which a depth of 105 fathoms has been found. As a See also:general See also:rule the slope from the English coast to the deepest parts of the Channel is more See also:regular than that from the French coast, and for that See also:reason, and in See also:consideration of the greater dangers to See also:navigation towards the French shore, the fairway is taken to lie between 12 and 24 M. from the See also:principal promontories of the English shore, as far up-channel as Beachy See also:Head. These promontories (the See also:Lizard, Start Point, Portland See also:Bill, St See also:Alban's Head, St See also:Catherine's Point of the Isle of Wight, Selsey Bill, Beachy Head, Dungeness, the See also:South See also:Foreland) demarcate a See also:series of bays roughly of sickle-shape, the shores of which run north and south, or nearly so, at their western sides, turn eastward somewhat abruptly at their heads, and then trend more gently towards the south-See also:east. On the French coast the arrangement is similar but reversed; Capes Grisnez, Antifer and La See also:Hague, and the Pointe du Sillon demarcating a series of bays (larger than those on the English coast) whose shores run north and south on the eastern See also:side, and have a gentler trend westward from the head. The configuration of the coasts is perhaps the See also:chief cause of the peculiarities of tides in the Channel. From the entrance as far as Portland Bill the See also:time of high water is found to be progressively later in passing from west to east, being influenced by the oceanic tidal stream from the west under conditions which are on the whole normal. But eastward of a line between Portland Bill and the Gulf of St Maio these conditions are changed and See also:great irregularities are observed. On the English coast between Portland Bill and Selsey a See also:double See also:tide is found. At Portland this double tide corresponds approximately with the time of See also:low water in the regular tidal progression, and the result is the occurrence of two periods of low water, separated by a slight rise known locally as " gulder." But farther east the double tide corresponds more nearly with the time of high water, and in consequence either the effect is produced of a prolonged period of high water, or there are actually two periods of high water, as at See also:Southampton. Various causes apparently contribute to this phenomenon. The configuration of the coast line is such as to See also:present at intervals barriers to the regular See also:movement of the tidal See also:wave (west to east), so that reflex waves (east to west) are set up. In the extreme See also:case at Southampton the tidal effect is carried from the See also:outer Channel first by way of of Spithead, the eastern strait. Finally the effect of the tidal stream entering the Channel through the Strait of Dover from the North Sea must be considered. The set of this stream towards the Strait of Dover from the east corresponds in time with that of the Channel stream (i.e. the stream within an area defined by Start Point, the Casquets, Beachy Head and the mouth of the See also:Somme) towards the strait from the west; the set of the two streams away from the strait also corresponds, and consequently they alternately meet and See also:separate. The area in which the See also:meeting and separation take See also:place lies between Beachy Head and the North Foreland, the mouth of the Somme and See also:Dunkirk. Within this area, therefore, a stream is formed, known as the intermediate stream, which, running at first with the Channel stream and then with the North Sea stream, changes its direction throughout its length almost simultaneously, and is never slack. Under these conditions, the time of high water eastward of Selsey Bill as far as Dover is almost the same at all points, though somewhat earlier at the east than at the west of this stretch of coast. The configuration of the French coast causes a very strong tidal flow in the Gulf of St Malo, with an extreme range at See also:spring tides of 42 ft. at St Germain, compared with a range of. 12 ft. at See also:Exmouth and 7 ft. at Portland. In the neighbourhood of See also:Beer Head and Portland and See also:Weymouth Roads the streams are found to See also:form vortices with only a slight movement. On the eastern (Selsey-Dover) See also:section of the English coast the maximum range of tide is found at See also:Hastings, with a decrease both eastward and westward of this point. See also:Westerly winds are most prevalent in the Channel. The total number of See also:gales recorded in the period 1871–1885 was 190, of which 104 were south-westerly. Gales are most frequent from See also:October to See also:January (See also:November during the above period had more than any other See also:month, with an average of 2.1), and most rare from May to See also:July. It appears that gales are generally more violent and prolonged when coincident with spring tides than with neaps. The winds have naturally a powerful effect on the tidal streams and currents, the latter being in these seas simply movements of the water set up by gales, which may themselves be far distant. Thus under the See also:influence of westerly winds prevailing west of the Iberian See also:Peninsula a current may be set up from the See also:Bay of See also:Biscay across the entrance of the Channel; this is called RenneIl's current. Fogs and thick See also:weather are See also:common in the Channel, and occur at all seasons of the See also:year. Observations during the period 1876-1890 at Dover, See also:Hurst See also:Castle and the Scilly Isles showed that at the two first stations fogs most frequently accompany anticyclonic conditions in See also:winter, but at the Scilly Isles they are much more common in summer than in winter, and accompany winds of moderate strength more frequently than in the case of the up-Channel stations. (O. J. R. H.) Salinity and Temperature.—The See also:waters of the English Channel are derived partly from the west and partly from the English" and French rivers, and all observations tend to show that there is a slow and almost continuous current through it from west to east. The western See also:supply comes from two See also:sources, one of which, the more important, is the relatively See also:salt and warm water of the Bay of Biscay, which enters from the south-west and has a salinity sometimes reaching 35.6 See also:pro mille (parts of salt per thousand by See also:weight); the other consists of a southerly current from the Irish Channel, and is colder and has a salinity of 35.0 to 35.2 pro mille, As the water passes eastwards it mixes with the fresher coastal water, so that the salinities generally rise from the shore to the central line, and from east to west, though south of Scilly Islands there is often a fall due to the influence of the Irish Channel. The mean See also:annual salinity decreases from between 35•4 and 35.5 pro mille in the western entrance to 35.2 pro mille at the Strait of Dover on the central See also:axis, and to about 34.7 pro mille under the Isle of Wight and off the Bay of the Seine. The English Channel may be divided into two areas by a line See also:drawn from Start Point to See also:Guernsey and the Gulf of St Malo. In the eastern area the water is thoroughly mixed owing to the action of the strong tidal currents and its comparatively small depth, and salinities andtemperatures are therefore generally the same from See also:surface to bottom; while westward of this line there is often a strongly marked See also:division into layers of different salinity and temperature, especially in summer and autumn, when the fresher water of the Irish Channel is found overlying the salt water of the Bay of Biscay. The salinity of the English Channel undergoes an annual See also:change, being highest in winter and spring and lowest in summer, and this change is better marked in the eastern area, where the mean deviation from the annual mean reaches o•3 pro mille, than it is farther west with a mean deviation of o•1 pro mille. There is also reason to believe that there is a regular change with a two-year period, years of high maximum and low minimum alternating with years of low maximum and high minimum. See also:Variations of long period or unperiodic also occur, which are probably, and in one case (1905) almost certainly, due to changes taking place some months earlier far out in the Atlantic Ocean. The mean annual surface temperature increases from between 1 I° C. and 11.5° C. at the Strait of Dover to over 12° C. at the western entrance). The yearly range in the eastern area is considerable, reaching 11° C. off the Isle of Wight and io° C. in the Strait of Dover; westward it gradually decreases to 5° C. a See also:short distance north-west of Ushant. The mean maximum temperature, over 16° C., is found under the English coast from Start Point to the Strait of Dover about the 1st of See also:September and off the French coast eastward of Cape la Hague about eleven days later. In the western area the maximum temperature is about 15° C. and occurs between September i and ir. The mean minimum surface temperature is between 5° C. and 6° C. at the eastern end, and increases to over 9° C. off the coast of Brittany. Owing to the thorough mixing of the water in the eastern area the temperatures are here generally the same at all depths, and the description of the surface conditions applies equally to the bottom. In the western entrance, on the other See also:hand, the bottom temperature is often much See also:lower than on the surface; the range here is also much less, about 3° C., and the maximum is not reached till about the 1st of October, or from three See also:weeks to a month later than on the surface. A detailed See also:account of the mean conditions in the English Channel will be found in See also:Rap. et proces-verbaux, vol. vi., and Bulletin supplementaire (1908) of the Conseil Permanent See also:International pour 1'Exploration de la Mer (See also:Copenhagen). (D. J. M.) See also:Cross-Channel Communication.—An immense amount of time and thought has been expended in the elaboration of schemes to provide unbroken railway communication between Great See also:Britain and the continent of See also:Europe and enable passengers and goods to be conveyed across the Channel without the delay and expense involved by transhipping them into and out of See also:ordinary steamers. These schemes have taken three See also:main forms: (I) tunnels, either made through the ground under the sea, or consisting of built-up structures resting upon the sea See also:bed; (2) See also:bridges, either elevated high above the sea-level so as to admit of the unimpeded passage of See also:ships under them, or submerged below the surface; and (3) See also:train ferries, or vessels capable of conveying a train of railway vehicles with their loads. A See also:tunnel was first proposed at the very beginning of the 19th See also:century by a French See also:mining engineer named Mathieu, whose See also:scheme was for a time favourably regarded by See also:Napoleon, but it was first put on a See also:practical basis more than fifty years later by J. A. See also:Thorne de Gamond (1807–1876), whose plans were submitted to the French See also:emperor in 1856. This engineer had begun to See also:work at the problem of cross-Channel communication twenty years previously, and had considered the possibility of a submerged tunnel or See also:tube resting on the sea-level, of See also:steam ferries plying between huge piers thrown out from both coasts, and of a See also:bridge, for which he prepared five different plans. He again brought forward his scheme for a tunnel, in a modified form, in 1867, and exhibited his plans in the Universal See also:Exhibition of that year. About the same time an English engineer, See also: He and Thorne de Gamond joined forces, and their plans were adopted by an international See also:committee whose See also:object was to popularize the idea of a tunnel both in England and France. Its See also:engineers on the English side were Lowe, See also:Sir See also: About the same time Zerah See also:Colburn produced plans for a tube constructed of loon ft. sections, which were to be built in dry See also:dock and then successively attached by a See also:ball and socket See also:joint to the completed portion, the whole being raised from the bottom and dragged out to sea, by the aid of a large number of ships, as each section was attached and launched., See also: Some authorities, such as Sir See also:Joseph See also:Prestwich, doubted whether the tunnel should be attempted in the chalk because of the likelihood of fissures being encountered while others who thought the chalk suitable were dissatisfied with the actual plans and formed a See also:rival " Anglo-French Sub-marine Railway Company." In 1882 another tunnel company made its See also:appearance. In 1874 the South Eastern Railway Company had obtained powers to sink experimental shafts on its See also:property between Dover and See also:Folkestone, and in 1881 to acquire lands, including the See also:beach and See also:foreshore, in that area in connexion with a Channel tunnel. These powers resulted, in 1882, in the formation of the Submarine See also:Continental Railway Company which in that year sought See also:parliamentary sanction for a tunnel, starting from a point west of Dover, at Shakespeare's Cliff; and at the same time the resuscitated Channel Tunnel Company applied for powers to make one from Fanhole, instead of St Margaret's Bay as in its former scheme. The whole question of the tunnel was then widely discussed and considered by various committees, the last of which—a joint select committee of the Lords and Commons—in 1883 expressed the See also:opinion by a See also:majority that it was " inexpedient that parliamentary sanction should be given to a submarine communication between England and France." This decision for the time being disposed of the question of making a tunnel, and though Sir See also:Edward See also:Watkin, one of its most prominent See also:advocates, brought bill after bill before See also:parliament to authorize experimental works in connexion with it, all were rejected. In 1882 the See also:government interfered with the operations then in progress, and they were ultimately discontinued. They included a driftway 7 ft. in diameter which was driven for a distance of about 2300 yds. eastwards under the sea at an inclination of 1 in 72 from the bottom of a shaft sunk to a depth of 164 ft. in the chalk See also:marl at Shakespeare's Cliff. About this time the Channel Bridge and Railway Company took in hand the See also:design of a bridge, the preliminary plans for which were exhibited in the See also:Paris Exhibition of 1889. The terminal points were Folkestone and Cap Grisnez, and for the See also:sake of facilitating the laying of the See also:pier See also:foundations it was proposed to take the bridge over the Varne and Colbart shoals. The main girders were to be nearly 59 yds. above the sea-level, the railway itself being more than 20 ft. higher 'still, and the spans were to vary in length between 540 and 1o8 yds. As the result of a survey of the sea bottom made in 189o, a modification in the line of the bridge was adopted, and it was taken See also:direct from Cap Blancnez to the South Foreland. It was found that in this way an excellent bottom would be obtained for the foundations, and the length of the bridge would be 3 M. less, the number of piers, by employing spans of 434 and 542 yds. alternately, being reduced to 72. The cost of this structure was estimated at £28,320,000, exclusive of See also:interest on See also:capital during the period of construction, which was put at seven years. The same company also worked out plans for a moving See also:chariot or See also:platform, capable of holding a railway train and supported by. long legs on a submerged See also:causeway or track constructed of steel or
armoured concrete 45 or 50 ft. below low-water level. No attempt has been made actually to carry out either this project or that of a bridge.
In 1905 the question of establishing a train ferry from Dover across the Channel was brought forward by the Intercontinental Railway Company, and in the following year the Channel Ferry (Dover) Act was passed authorizing the work. About the same period the Channel Tunnel Company, which had amalgamated with the Submarine Railway Company, awoke to activity and started a See also:campaign in favour of its scheme; but the bill which it promoted was opposed by the government and accordingly was withdrawn in See also: Eng. vol. 33 (1882); W. See also:Boyd See also:Dawkins, " The Channel Tunnel," See also:Manchester Geol. See also:Soc., May 1882, and Brit. Assoc. See also:Rep. (1882, 1899); E. de Rodakowski, The Channel Ferry (See also:London, 1905). (H. M. Additional information and CommentsThere are no comments yet for this article.
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