Hy4rographi^y and the Ari qf Navigaiwrt, 'W 



derate. The deviations from a uniform level which they can 

 occasion ought hkewise to be inconsiderable. But it seems diffi- 

 cult to believe, that the vertical iall of a metre, for example, or 

 ^ven two metres, can produce currents which do not entirely 

 disappear after a passage of many hundred leagues. 



I have stated that the trade-winds, on account of their want 

 of intensity, seem but little likely to produce any considerable 

 swelling in the waters of the ocean. I will even go further than 

 this, and prove that, in point of fact, the seas from which cur- 

 rents appear to emanate, are exactly, or very nearly, of the same 

 level as those which the currents traverse. 



It has been indisputably proved by M. Lepere, in the obser^ 

 vations made during the Egyptian expedition, that the level of 

 the Mediterranean, near Alexandria, is lower by 8% 1 than 

 the low water-level of the Red Sea near Suez, and 9™, 9 than 

 the high water leveL 



This is certainly a very great difference of level between two 

 seas which may be considered as communicating with each other ; 

 for, on the one hand, the Mediterranean opens into the Atlantic 

 by the Straits of Gibraltar ; on the other, the Red Sea opens 

 into the Indian Ocean by the Straits of Babelmandel ; and, in 

 the third place, the Atlantic and Indian Ocean become blended 

 with each other at the Cape of Good Hope. It is very far 

 from my intention to depreciate what is curious or interesting 

 in such a result as this ; but I must be allowed to say, that it 

 throws no light on the disputed question of currents, for, to ren- 

 der the explanation admissible, there ought to be a sensible diffe- 

 rence between the level of two contiguous seas, between that 

 from which the current issues, and that into which it flows. 



Does not precisely such a difference as this, it may be asked, 

 exist between the Mexican Sea, in which the Gulf Stream ori- 

 ginates, and the part of the Atlantic Ocean which washes the 

 eastern side of the Floridas and Georgia ? 



The inhabitants of the Isthmus of Panama believe, but with- 

 out proof, that the South Sea is higher than the Atlantic Ocean. 

 Franklin, Rennel, &c. likewise admit a difference of elevation, 

 but in a contrary sense. M. de Humboldt confirmed this latter 

 opinion by some barometrical observations made at Cumana, 

 Carthagena, and Vera Cruz, compared with others made at 



