144 THE PHYSICAL GEOGRAPHY OF THE SEA. 



duriDfi^ my researches connected with the wind and current charts, 

 and the result has satisfied nie that it is neither a dangerous nor a 

 constant current, notwithstanding older writers. Horsburgh, in 

 his East India Directory, cautions navigators against it ; and Keith 

 Johnston, in his grand Physical Atlas, published in 1848, thus 

 speaks of it : 



" This current greatly impedes the progress of those vessels 

 which cross the equator west of 23° west longitude, impelling 

 them beyond Cape St. Roque, when they are drawn tow^ard the 

 northern coast of Brazil, and can not regain their course till after 

 weeks or months of delay and exertion." 



So far from this being the case, my researches abundantly prove 

 that vessels which cross the equator five hundred miles to the w^est 

 of longitude 23° west have no difficulty on account of this current 

 in clearing that cape. I receive almost daily the abstract logs of 

 vessels that cross the equator west of 30° w^est, and in three days 

 from that crossing they are generally clear of that cape. A few 

 of them report the current in their favor ; most of them experience 

 no current at all ; but, now and then, some do find a current set- 

 ting to the northward and westward, and operating against them 

 at the rate of twenty miles a day. The inter-tropical regions of 

 the Atlantic, like those of the other oceans (§ 270), abound with 

 conflicting currents, which no researches yet have enabled the 

 mariner to unravel so that he may at all times know where they are 

 and tell how they run, in order that the navigator may be certain 

 of their help when favorable, or sure of avoiding them if adverse. 



277. I may here remark, that there seems to be a larger flow 

 of polar waters into the Atlantic than of other waters from it, and 

 I can not account for the preservation of the equilibrium of this 

 ocean by any other hypothesis than that which calls in the aid of 

 under currents. They, I have no doubt, bear an important part 

 in the system of oceanic circulation. 



Admiral Sir Francis Beaufort, the venerable hydrographer of 

 England, made, when in command of her Britannic majesty's 

 frigate Frederikstccn, in the Mediterranean, some interesting ex- 

 periments upon under currents, which I should be glad to see re- 

 peated in other parts of the sea, especially between the tropics, in 

 the Atlantic, Pacific, and Indian Oceans, and wherever the water 

 is remarkably transparent. That officer says : 



