COASTAL CURRENTS ALONG THE ATLANTIC COAST OF 

 THE UNITED STATES 



INTRODUCTION 



The area covered by this discussion stretches along the Atlantic 

 coast of the United States from Maine to Florida. It lies for the most 

 part inside the 30-fathom depth curve and extends into a number of 

 the larger sounds and bays that indent the coast. Although a detailed 

 knowledge of the currents in this area is of great importance to navi- 

 gators, the large expense generally involved in securing adequate cur- 

 rent observations in unprotected waterways long prevented the acqui- 

 sition of that knowledge. 



During the last three decades, however, there has been in effect a 

 cooperative arrangement between the Coast and Geodetic Survey and 

 the Lighthouse Service whereby long series of current observations 

 have been secured at lightship stations. Current measurements along 

 our Atlantic coast have been made at approximately 50 such stations. 

 Continuous series of hourly observations covering a year or more have 

 been obtained at about half of these and a number of months at each 

 of the others. 



Much information derived from the observations has been published 

 in various forms in the annual current tables and other publications 

 of the Coast and Geodetic Survey. During the past few years many 

 new reductions have been made of the accumulated records. The 

 results of these reductions correlated with those previously obtained 

 are given in considerable detail in the pages that follow. An attempt 

 is made to present the material in such forms that with the aid of the 

 explanatory text it will be intelligible to all users, and of value to the 

 mariner and the fisherman as well as to the oceanographer and the 

 tidal expert. 



METHOD OF OBSERVING 



In general, the process of observing currents consists of measuring 

 at fixed intervals of time, such as hourly or half-hourly, the velocity 

 of the current; noting the direction the current is flowing at each 

 measurement of velocity; and recording the direction, the velocity, 

 and the time at which each measurement is made. Various means 

 of taking such observations have been employed. The current pole 

 method of observing was used exclusively on all the lightships at which 

 current measurements were made. 



The current pole is a wooden pole so weighted with lead that it will 

 submerge for most of its length and assume a vertical position when 

 placed in the water. The pole is attached to a line and allowed to 

 drift with the current while an observation is being made. The line, 

 known as a current line, is marked in principal and secondary divi- 

 sions, each secondary division being one-tenth of a prmcipal division. 

 The length of each prmcipal division bears the same ratio to a nautical 



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