Basic Principles of the General Oceanic Circulation 569 



currents. Since the thermal equator remains in the Northern Hemisphere throughout 

 the whole year these currents are not symmetrical about the geographical equator. 

 The southern boundary of the North Equatorial Current lies between 6° N. and 7° N. 

 in winter and between about 9° N and 11 ° N. in summer. It is much stronger in winter. 

 At its southern boundary the current at each location has a purely zonal direction and 

 constant speed, while its velocity increases steadily towards the west. Off the Philli- 

 pines (north of Mindanao) the strong current divides : one branch flowing northward 

 to become the Kuroshio and the other turning sharply southward into the Equatorial 

 Counter Current. Off the east coast of Mindanao it flows southwards with a 100% 

 constancy (Schott, 1939, see also Puls, 1895). 



The South Equatorial Current covers the wide south-east trade wind belt between 

 about 5° N. and 40° S. The greatest velocities and constancy again lie along the 

 northern border between 5° N. and 5° S. and, as in the Atlantic, a double current core 

 is occasionally present. By this a long and narrow tongue of extremely low tempera- 

 ture is caused in the thermal field in the eastern part of the Pacific west of the Gala- 

 pagos Islands. These areas of cold water are associated with the occurrence of 

 eastward ship's displacements within the South Equatorial Current. Similar ship's 

 displacements are occasionally observed in the Atlantic. West of New Guinea and the 

 Solomons the South Equatorial Current during the northern summer is a torrent 

 current extending almost as far as Halmahera ; it supplies the main water mass of the 

 counter current. Off the east coast of Australia the South Equatorial Current bends 

 and is called from thereon the East Australian Current which corresponds to the 

 Agulhas Current in the Indian Ocean. 



All the year long a well-developed counter current is inserted between the two 

 Equatorial Currents. During the northern winter it is weak and narrow, except in its 

 starting area in the west, but during the northern summer especially during August 

 and September it flows with great Constance from Mindanao-Palau-Halmahera to 

 Panama (almost 8000 nautical miles) with a width of about 300 miles between 

 5° N. and 10° N. It is separated from the Equatorial Currents by well-defined bound- 

 aries especially on the northern side. 



The Kuroshio is a continuation of the North Equatorial Current and in many 

 respects an important phenomenon for Eastern Asia. A review of what is known of 

 this current and a comparison with the Gulf Stream system with numerous references 

 has been given by WiJST (1936^, see also, Uda and Okamoto 1930, 1931 ; Uda, 1933). 

 In summer it starts flowing northward east of Formosa with a velocity of 24-36 

 nautical miles in 24 h and a width of about 300 nautical miles. Then it runs west of 

 the Ryukyu Islands between the Ryukyu Ridge and the East China shelf with decreas- 

 ing width and correspondingly increasing speed (36-48 nautical miles in 24 h) until it 

 branches south of Japan ; one branch, the Tsusima current enters the Sea of Japan and 

 flows north-north-west, the other, the proper Kuroshio, flows with a reduced width 

 along the south-eastern coast of Japan. Between 31 ° and 35° N. it is only about 150 km 

 wide but its velocity rises to 48-56 nautical miles per day. Its left-hand boundary is 

 sharply defined but the right-hand one (oceanic side) is blurred. Here, like the Gulf 

 Stream, it has a weak counter current. It turns abruptly eastwards towards the open 

 ocean at 36° N. off the Boso Peninsula with an almost invariable width but with 

 gradually decreasing velocity (48-24 nautical miles per day). This deflection of the 



