284 J. 8. Brown — Relation of Sea Water 



In any case g — 1 will be the difference in specific gravity 

 between the fresh and salt water. Herzberg gives the 

 specific gravity of the North Sea as 1.027, whence h = 37t. 

 Drillings on Norderney and other islands near by gave 

 results varying but a few meters from those derived by 

 the formula, but it is not clear whether the salt water 

 encountered at the expected depth had approximately the 

 composition of sea water or was merely too salty for use. 

 Herzberg states, further, that the results are sometimes 

 greatly modified by the fineness or coarseness of the 

 sands, indicating that a factor due to porosity is involved. 

 The theory appears to apply particularly to small islands 

 and narrow land masses which consist of freely pervious 



Fig. 3. 



Sea"^ tef 



Fig. 3. — Section of the island of Norderney, showing the application of 

 Herzberg 's theory. (From Herzberg.) 



material, especially sand, and even to these only to a 

 certain extent. However, Herzberg 's paper appeared at 

 a time when there was great interest in coastal water 

 supplies in Holland and Belgium, particularly at Amster- 

 dam, and was widely quoted and much discussed by 

 Dutch, Belgian, and French writers. The law of equi- 

 librium between salt and fresh water is frequently 

 referred to as the "theory of Herzberg.' ' 



Nature of tine -contact between fresh and salt water. 



Along coasts there is a continual diffusion of salts from 

 the sea water into the fresh ground water of the land and 

 an actual movement of fresh ground water seaward. 

 There must exist a transition zone in which equilibrium 

 is established between these opposing forces. The loca- 

 tion and nature of this zone are determined in part by 



