86 THE OCEAN. 



the shores of the continent, sends out into the little bays currents of 

 a third order, which also complete their circular movement, like the 

 Gulf-stream and the Kuro-Sivo ; and so by lateral transmission, the 

 circulation of the waters is continued from oceans to gulfs, from 

 gulfs to bays, and from these to the creeks. These secondary 

 currents, however, are usually much less regular than the general 

 currents, and navigators have ascertained that at times RennelFs 

 current has flowed in a completely reversed way to its normal 

 direction.* 



Secondary currents generally move in a course exactly opposite 

 to that of the principal stream, of which they are only a branch bent 

 back on itself. Either permanently or temporarily they are found in 

 all seas, open or inland, in all gulfs and bays of the ocean. Even 

 the sea of the Antilles, the waters of which are carried almost en 

 masse towards the Gulf of Mexico, presents at its western extremity 

 a permanent current, which tends from the shores of the isthmus to 

 those of Columbia. A vessel drifted by the principal current into the 

 neighbourhood of Nicaragua, would only have to ascend to Colon, and 

 then abandon itself to the waves in order easily to accomplish its re- 

 turn voyage, borne by the waters which flow incessantly in the 

 direction of Carthagena and Santa ^klarta. Many lazy seamen never 

 pass from the ports of the isthmus to those of Terra Firma in any 

 other way. Regardless of time, they let themselves be rocked by the 

 billows without even taking the trouble to hoist the sails. Their 

 bark, slower than a tortoise, advances at the most but a mile an 

 hour, and after eight or ten days spent on the passage, they finally 

 perceive the bluish mountains of New Granada, and its sandy shores 

 shaded by cocoa-nut trees. 



There are some currents which are evidently produced by a dis- 

 turbance of equilibrium between two levels. Thus the Baltic Sea, 

 which receives more water by the contributions of rivers than it loses 

 by evaporation, must necessarily distribute its superfluity in the 

 North Sea through the straits of the Sound and the two Belts. 

 Nevertheless, these outlets being large and deep enough to diffuse 

 the superabundant water in a little time, the current is not per- 

 manent. Waves from the North Sea, driven into the Baltic by the 

 westerly winds, frequently meet it, and from this conflict of waters 

 arise local and unexpected movements, dangerous to ships. Every 

 four days the waters on the surface flow on an average for forty- 

 eight hours towards the Cattegat, then flow back into the Baltic for 

 * Gareis and Becker, Physiographie des Meeres. 



