FOREWORD 



The following paper has been compiled from a series of lecture 

 notes made by the writer when he took an advanced course on ocean- 

 ography under Prof. Bjorn Helland-Hansen, Geo-Physical Institute, 

 Bergen, Norway. Writers of textbooks on oceanographj", fail from 

 time to time, due to the rapid growth of this science, to keep pace 

 in print with the newest methods in practice. The need for the 

 appearance of the present treatise is emphasized when it is realized 

 that a complete exposition of the methods elucidated herein has never 

 before, to the WTiter's knowledge, been collected in a single publica- 

 tion, and the particular hydrographical information, prior to this, has 

 been unavailable short of personal instruction in Europe. Although 

 the illustrations to be found tliroughout the paper are in most cases 

 examples taken from observations of the International Ice Patrol off 

 Newfoundland, and although the bulletin is intended especially to 

 assist the prosecution of Ice Patrol service, the application of the text 

 is, nevertheless, quite broad in its scope. It is therefore recom- 

 mended to the attention of all students interested in the subject of 

 physical oceanography. 



The foundation upon wiiich this paper rests was first laid down by 

 Prof. V. Bjerknes, (see "Dynamic Meteorology and Hydrography,'' 

 Carnegie Institution publications, Wasliingtpn, 1910-11). In the lines 

 of history which record attempts to apply mathematics to the natural 

 sciences tliis treatise by Bjerknes stands out as one of the most 

 successful and progressive. A perusal of the book can not fail to 

 impress one with the infinite care and exactitude with which the 

 theories have been presented and the exposition developed. It 

 is a model of scientific treatment, but he who is searching for a 

 practical method directly applicable to a hydrographical problem 

 is bound to note the absence of just this sort of pertinent information. 

 Since the time when Bjerknes' theories became recognized by scien- 

 tists there have been a few oceanographers, especially Helland-Hansen, 

 Nansen, Ekman, and Sandstrom, who have done much to give the for- 

 mulae of motion a practical application to the sea. As a result of such 

 development we are now supplied with a scientific method whereby 

 if the temperature and salinity of the ocean are given from several 

 known depths and stations the direction and velocity of the currents 

 even in the deep water off soundings can be computed and mapped. 

 In this connection it may be of interest to know that the currents 

 calculated from the observational data collected in 1922 off the 

 Grand Banks have been found to agree very closeh^ with the drifts 

 of the icebergs of that same year and region. 



(V) 



