Geography of the Sea. 141 



nel soon after made the division of drift and stream currents. 

 The objections which have appeared against the wind theory 

 have been met with the reply that the present state of oceanic 

 movements is the result of the work done by the winds in count- 

 less thousands of years. 



Current phenomena is briefly summarized as follows by one of 

 the latest authorities on the subject : 



1. The greater portion of the current movement of the ocean 

 must be regarded as a drift, produced by the prevailing winds, 

 whose mean direction and force are the measures for the mean 

 set and velocity of the current. 



2. Another group of currents, and in fact a fraction of all cur- 

 rents, consists of compensating or supply streams, created by the 

 necessity of replacing the drifted water in the windward portion 

 of the drift region. 



3. A third group results from drifts deflected by the config- 

 xiration of the coasts ; these which are denominated free cur- 

 rents, quickly pass into compensating streams. 



4. The deflecting force of the rotation of the earth is consid- 

 ered as of subordinate importance, but may have some influence 

 on currents that are wholly or in part compensating or free. 



Late investigations of the Gulf Stream by the TJ. S. Coast 

 Survey give interesting facts in regard to that notable current. 



A satisfactory explanation of the cause of the stream has not 

 yet been found, but many believe, with Franklin, that the power- 

 ful trade drift entering the Gulf of Mexico through the broad 

 channel between Yucatan and Cuba presses the water as a strong 

 current through Florida Strait, where the stream is turned to the 

 northward along the coast. Since 1 850 American naval oflicers 

 have added greatly to our knowledge of the characteristics of 

 this stream, particularly within the last decade, during which 

 notable investigations have been carried on by Commanders 

 Bartlett and Sigsbee and Lieut. Pillsbury, U. S. N., under the 

 direction of the U. S. Coast Survey, and by Lieutenant Com- 

 mander Tanner, U. S. N., in the Fish Commission steamer Alba- 

 tross. 



Of special importance are the valuable and interesting results 

 in regard to tidal action in the stream obtained by Lieut. Pills- 

 bury, U. S. N., in the Coast Survey steamer Blake, from observ- 

 ations begun by him in 1885 at the narrowest part of Florida 

 Strait, between Fowey Rocks and Gun Cay (Bah.), and continued 



