348 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY. . 



influence. It is frequently traced for a thousand miles or more 

 out upon the ocean. For instance, the action of the sun's rays 

 upon the great deserts and arid plains of Africa, in the summer 

 and autmnnal months, is such as to he felt nearly across the At- 

 lantic Ocean between the equator and the parallel of 13^ north. 

 Between tliis parallel and the equator, the north-east trade-wiads, 

 during these seasons, are arrested in their course by the rainy 

 seasons and heated plains of Africa, as observation shows they are 

 in India, and instead of " blo^wg home " to the equator, they stop 

 and ascend over the desert sands of the continent. The south-east 

 trade-wmds, arriving at the equator durmg this period, and finding 

 no north-east trades there to contest their crossing the line, con- 

 tinue their course, and blow liome as a south-west monsoon, where 

 they deposit theh moistm-e and ascend. These southwardly mon- 

 soons bring the rams which divide the seasons in these parts of the 

 African coast. The region of the ocean embraced by these mon- 

 soons is cuneiform in its shape, ha\TQg its base resting upon Africa, 

 and its apex stretcliing over till mthin 10^ or 15° of the mouth of 

 the Amazon. Indeed, when we come to study the effects of South 

 America and Africa (as developed by the Wind and Current Charts) 

 upon the wiuds at sea, we should be .led to the conclusion — had the 

 foot of civilized man never trod the mterior of these two continents 

 — that the climate of one is humid ; that its valleys are, for the 

 most part, covered with vegetation, which protects its sm-face from 

 the sun's rays ; while the plains of the other are arid and naked, 

 and, for the most part, act hke furnaces m dra^^dng the winds from 

 the sea to supply au' for the ascendmg columns which rise from its 

 over-heated plams. Pushing these facts and arguments still farther, 

 these beautiful and interesting researches seem already sufficient 

 almost to justify the assertion that, were it not for the great desert 

 of Sahara and other arid plains of Africa, the western shores of that 

 continent, mthin the trade-w^ind region, would be almost, if not 

 altogether, as rainless and sterile as the desert itself. 



677. Lieutenant Jansen has called my attention to a vein of 

 A "Gulf stream" in "^^'ind which forms a current in the air as remark- 

 the air. ^j^j^ ^g |-]^^^ q£ |.j^g Q.^ Stream is in the sea. This 



atmospherical Grulf Stream is m the south-east trade-wmds of the 

 Atlantic. It extends from near the Cape of Good Hope, in a 

 dkect Ime to the equator, on the meridian of Cape St. Koque (Plate 

 VIII.). The homeward route fi'om the Cape of Good Hope hes 

 in the middle of this vein ; in it the winds are more steady than 



