110 THE PHYSICAL GEOGRAPHY OF THE SEA. 



to this theory, the land and sea breezes arise. Yet there are other 

 tropical regions where the land and sea breezes, even in the rainy- 

 season, regularly succeed each other. 



248. " The warming and the radiation alone are therefore not 

 sufficient to explain all the phenomena of land and sea breezes, 

 and other causes — electricity, rain, etc., appear to have an influ- 

 ence upon the regularity of the land winds.* 



249. " Upon the coast of Africa, the land-breeze is universally 

 scorching hot, but the sea-breeze is cool and refreshing. When 

 this is the case, the land-breeze certainly can not be occasioned 

 by the cooling of the earth by radiation. When we shall have 

 brought together all the observations upon the various phenomena 

 which the land and sea breezes afford, then we shall be able to 

 begin to found upon facts a theory which shall explain the varied 

 phenomena. Thus, among other things, upon the west coast of 

 Africa, from 0^ 21' S. to 15° 24^ S., according to Thomas Miller,t 

 from June to October, and, above all, in July, there are heavy 

 dews, and when the dews are very heavy, then the land and sea 

 breezes are invariably feeble — sometimes very faint." 



250. [Lieutenant Jansen's remarks are both instructive and sug- 

 gestive. It is true that a given difference of temperature between 

 land and water, though it may be sufficient to produce the phenom- 

 ena of land and sea breezes at one place, will not be adequate to the 

 same effect at another ; and the reason is perfectly philosophical. 



251. It is easier to obstruct and turn back the current in a 

 sluggish than in a rapid stream. So, also, in turning a current of 

 air first upon the land, then upon the sea — very slight alterations 

 of temperature would suffice for this on the west coast of Africa, 



* My observations lead me to suspect that the position of the moon is also herein 

 concerned. In the eastern outlet of Sourabaya, during the east monsoon, there is at 

 full moon little land-breeze, and at new moon little sea-breeze. I afterward made the 

 same observation in the Gulf of Darien. Feb. 4, 1852.— At the Road of Carthagena 

 (New Granada), full moon, sea-breeze north, under reefed top-sail, fresh gale ; at 11 

 P.M., feeble and easterly. Feb. 5.— 11 A.M., sea-breeze grows faint. 1 P.M., 

 stronger, and between 5 and 6 P. M. fresh gale ; double-reefed top-sail. Each day 

 somewhat later and less hard. Thermometer varying between 79° and 80°. Barom- 

 eter varying between 763° and 759°. Upon leaving Chagres, with new moon, it was 

 by day mostly feeble. — Jansen. 



t Nautical Magazine for June, 1855. — Jansen. 



