236 



DEPAKTMEyT OF THE NAVAL SERVICE 



caused by the water in the upper layer having its current there directed vertically 

 downwards, and striking against the separating surface. At the other end of the 



'^ 5CH0^4E:N 



. 



RUGEN 



Fig. 10. — Wind and distribution of temperature, with 

 probable movement of the water, in tlie .southern part 

 of the Baltic, 1 August 1907. 



reservoir also, the separating surface is seen to be slightly rounded off where the 

 current turns. That corresponding deformations of the surface layer occur in the 

 sea will be seen from the hydrographical sections in figs. 16 and 17. 



5-America 

 m. ^O^Longw 30 



<- 



20 



A ^ SS/^T" 



-«- 



Africa 

 10* Long. E 



Fig. 17. — Wind, lij'^ isotherm, and probable movement of tlu^ water between 

 Africa and S. America, lat. 20^' S. 



Owing to the circulation in the surface layer in iig. 15, the water therein 

 remained very homogeneous. From the continual friction upon the layer beneath, 

 the surface layer absorbed into itself some of the water adjacent, and thus gradually 

 increased in volume. The longer the experiment lasted, the thicker and Salter would 

 the surface layer grow. The same thing would probably take place in the sea with a 

 continual wind. 



Heavy water 



Fig. 18. — Experiment illustrating current opposed to the 

 wind on tiie weather toward shore. 



I now poured a small quantity of fresh water into the water already in the tank, 

 as answering to rainfall, or inflow from rivers and streams into the sea. This fresh 

 water was driven by tlie current of air towards the end of the tank against which the 

 wind was blowing, forming a triangular inset there, as shown in fig. 18. It was here 

 distinctly subjected to two forces, firstly the wind, endeavouring to bring about a cir- 

 culation where the surface water moves in the direction of the wind, and secondly the 

 current beneath, seeking to induce a circulation where the surface water moves against 

 the direction of the winrl. The latter, however, obtained the mastery, as shown in 



