162 . OBSERVATIONS ON THE WINDS. 



The rainy season* ends in very violent squalls, with intervals of ealm, of 

 which there are at least two, and frequently more, during the twenty- four 

 hours ; and we remarked that they generally happen on the rising or set- 

 ting of the sun or moon. In the country, these squalls are generally called 

 Tornados ; but, according to the best information, the Tornado, properly 

 speaking, is to be met with only to the Southward of Cape Verga. They 

 generally begin to form themselves in the N.E. or E.N.E. quarter of the 

 horizon, which seems completely on fire during an hour or more. The 

 storm then gradually shifts round to East and E.S.E., becoming darker in 

 the horizon. Having arrived at S.E,, it attains its full vigour, when 

 thunder and lightning become incessant. A moment of absolute calm then 

 takes place, which is caused by the obstruction which the usual winds from 

 the N.W. meet with from this immense mass of clouds. Shortly after, a 

 small arch is formed at the horizon, which increases and rises rapidly. 

 The more defined the edge of this arch appears, the more violent will be 

 the storm, as it is a proof that the column of air has divided much heavier 

 clouds, and is more confined. When the summit of this arch has attained 

 an altitude of about 45°, the hurricane bursts forth, and torrents of rain 

 immediately follow. The crisis of its greatest violence generally lasts from 

 15 to 20 minutes ; it afterwards gradually becomes weaker ; and, finally, 

 nothing remains but rain, attended with very little wind. It then shifts 

 round from S.E. to W.S.W., then to the quarter from which the usual winds 

 blow, to exhaust itself to the Northward in another squall from the S.E. 



The rainy season, at any place, continues from four to six months, accord- 

 ing to its proximity to the Equator, and the Tornados continue to decrease, 

 both in frequency and violence, during the two latter months of the season. 

 In ten days or a fortnight after the sun has passed the zenith of anyplace 

 on his way to the South, it is considered as free from bad weather. On 

 the 15th of November, a gun is fired at Goree, which announces the return 

 of the fine season. 



The squalls here spoken of, and the winds which precede or follow them, 

 generally occupying so very small a portion of the year, may be considered 

 as momentary convulsions in a state of climate almost unchangeable ; a 

 sky nearly always serene, and generally clear. 



On the greater part of the African coast, from Cape Bojador to the Isles 

 de Los, regular winds blow, and no rain ever falls during eight months. 

 The prevailing winds in this country blow from N.E. to N.W. ; it may, 

 therefore, be said that they follow the direction of the coast from North to 

 South, and that they seldom vary from the limits here assigned. 



The dry season commences in the latter part of October at Senegal ; a 

 little later at Goree ; and at each intermediate place toward the Equator 

 it becomes gradually later. It is not till the beginning of December that 

 its return is observed in the parallel of the Isles de Los. 



• Captain Adams, in his sketches, says that the Wet Season, North of the Equator, 

 commences in the month of May, and terminates in July, when the Dry Season beginr, 

 although heavy showers of rain fall during the months of October and November, which 

 enable the Africans to reap a second harvest of maize ; but the rains commence and ter- 

 minate six weeks earlier near the Equator than at the Northern boundary, where the 

 periodical rains cease. 



