Hydrography, and the Art of Navigation. 4& 



1*^, That the mean level of the Pacific Ocean, at Panama, is 

 from 3,52 English feet (l*",!) higher than the mean level of 

 the Atlantic Ocean at Chagres ; 



^dy That at the moment of high tide, the ocean on the west- 

 ern side of the isthmus, is from 13.55 feet (4™,! 3) higher than 

 on the western side. 



3(/, That at the moment of low water, on the same coasts, the 

 Pacific Ocean, on the contrary, is lower than the Atlantic 6.51 

 feet (l'",98). 



These observations seem, then, to confirm the opinion long 

 since adopted, that the mean level of the South Sea is more ele- 

 vated than the mean level of the Atlantic Ocean ; but the differ- 

 ence, instead of being enormous, as was supposed, is only eleven 

 decimetres. It may even be allowed us to suppose, without in- 

 justice to the merits of Messrs Lloyd and Palmare, that, in carry- 

 ing on their operations in a wild country environed with diffi- 

 culties ; in traversing a line, the total extent of which, including 

 sinuosities, is eighty-two miles (33 leagues), and that, in taking 

 levels at 935 stations, they may have erred to the small extent 

 of a metre. From this it follows, that there is nothing to proVe 

 that a sensible difference exists between the mean levels of the 

 tvvo great seas which communicate with each other by the Straits 

 of Magellan and Cape Horn. * 



The work of Messrs Lloyd and Palmare, in so far as it applies 

 to the explanation of the rapid current which precipitates itself 

 from the Gulf of Mexico into the ocean by the Straits of Bahama^ 

 advances as a hypothesis that the South Sea and Atlantic Oceans, 

 viewed as a whole, form a surface of the same level. We will 

 escape from this difficulty by relating the results of some obser- 

 vations made in Florida a few years since by the French officers 

 appointed by the American Congress to survey the line of a 

 canal designed to unite the river St Marie, on the Atlantic, with 

 the bay of Appalachicola, on the Gulf of Mexico. 



• If, after the leanied memoirs of M. de Humboldt, it is still necessarj 

 to return to the truly astonishing depression that the Cordillera of America 

 presents in the Isthmus of Panama, before again assuming its full majesty in 

 Mexico, I would remark that the most elevated point of the transverse line 

 levelled by Messrs Lloyd and Falmare, is only 633 English feet above the 

 level of the sea. 



VOL. XXI. NO. XLI. — JULY 1836. D 



