INFLUENCE OF THE GULF STREAM UPON COMMERCE. 69 



the Constitution of the United States to the protection given by 

 legislation to Northern interests. But I think these statements 

 and figures show that this decline was in no small degree owing 

 to the Gulf Stream and the water thermometer ; for they changed 

 the relations of Charleston — the great Southern emporium of the 

 times — removing it from its position as a half-way house, and 

 placing it in the category of an outside station. 



111. The plan of our work takes us necessarily into the air, for 

 the sea derives from the winds some of the most striking features 

 in its physical geography. Without a knowledge of the winds, 

 we can neither understand the navigation of the ocean, nor make 

 ourselves intelligently acquainted with the great highways across 

 it. As with the land, so with the sea ; some parts of it are as un- 

 traveled and as unknown as the great Amazonian wilderness of 

 Brazil, or the inland basins of Central Africa. To the south of a 

 line extending from Cape Horn to the Cape of Good Hope (Plate 

 VIII.) is an immense waste of waters. None of the commercial 

 thoroughfares of the ocean lead through it ; only the adventurous 

 whaleman finds his way there now and then in pursuit of his 

 game ; but for all the purposes of science and navigation, it is a 

 vast unknown region. Now, were the prevailing winds of the 

 South Atlantic northerly or southerly, instead of easterly or west- 

 erly, this unplowed sea w^ould be an oft-used thoroughfare. 



112. Nay, more, the sea supplies the winds with food for the 

 rain which these busy messengers convey away from the ocean to 

 "the springs in the valleys which run among the hiUs." To the 

 philosopher, the places which supply the vapors are as suggestive 

 and as interesting for the instruction they afford, as the places are 

 upon which the vapors are showered down. Therefore, as he who 

 studies the physical geography of the land is expected to make 

 himself acquainted with the regions of precipitation, so he who 

 looks into the physical geography of the sea should search for the 

 regions of evaporation, and for those springs in the ocean which 

 supply the reservoirs among the mountains with water to feed the 

 rivers ; and, in order to conduct this search properly, he must con- 

 sult the winds, and make himself acquainted with their " circuits." 

 Hence, in a work on the Physical Geography of the Sea, we treat 

 also of the x\tmospheke. 



