Page:Africa by Élisée Reclus, Volume 3.djvu/170

 134 WEST AEEICA. of the dyke. But five years afterwards it had returned to Camel Point, close to Saint-Louis, in 1864 retreating over 2,000 yards southwards, and in 1884 again retiring to a point south of Gandiole. The depth of the channel seldom exceeds 13 or 14, and seldom falls below 8 feet, being shallowest from November to February, and deepest in April and May, at the end of the dry season. The depth is increased 6 or 7 feet by the tides ; but in rough weather the bar is almost inaccessible to shipping, which has at times to wait for weeks either off the roadstead or within the port of Saint-Louis. To obviate this and other inconveniences it has been proposed to create a permanent channel by means of a curved pier forming a continuation of the left bank of the river. JNorth of the Senegal there are no perennial rivers in the territory politically assigned to France. Nor are there now any streams for a stretch of 180 miles south of the bar, until the Salum is reached. Eut according to a well-founded local tradition, the Senegal itself seems to have formerly continued its southern course parallel with the coast under the shelter of the Cayor dunes as far as the Bay of Dakar, below Cape Verd. According to Wendling's recent observations the Cayor formations appear to have been originally fluvial deposits, which became attached to the islet of Dakar, and were afterwards covered by marine sands. South of Cape Yerd the shore -line curves round towards the south-east, thus describing an arc corresponding to that of the Cayor dunes. Here a few streamlets reach the coast ; but north of the Gambia the seaboard is broken only by the large island- studded estuary, which is sheltered from the sea by the long peninsula terminating at Point Sangomar, and which towards the north-east mingles its waters with those of the Salum, a coast-stream navigable for some 60 ndles. Climate of the Senegal Basix. The Senegal year is divided into two periods of nearly equal length, the dry season, answering to the summer of the southern hemisphere, from the end of November to the beginning of June, and the wetj which is also the hottest, for the rest of the year. During the former the trade winds prevail, occasionally interrupted near the sea by local breezes blowing from the north-west and west. Thanks to these atmospheric currents and to the cool marine current setting from the north, the temperature is relatively moderate along the seaboard, oscillating at Saint-Louis and at Goree round a mean of from 68^ to 70° F. But in the interior this dry season is again divided into two periods corresponding somewhat to the winter and spring in Europe. The winter, if not cool, is at least almost temperate (77° F.) ; but in the spring, when the hot east Saharian winds pre- dominate, the glass stands normally at 90° F. The changes from season to season are usually ushered in by the " tornadoes," small local cyclones, generally lasting from fifteen minutes to an hour, and nearly always wheeling from the south-east and east round to the north and west, reversing the direction of the normal wind. They are violent gales which, when unaccompanied by rain, may even become dangerous.