Tides of the Oceans 491 



hemisphere and the high amplitudes do not support this interpretation. The 

 phases from the Tasman Sea and Coral Sea to New Guinea and New Ca- 

 ledonia remain constant at about 300 3 . The transition to the previously 

 mentioned large area of nearly constant phase of 120-150° takes place in the 

 western part by a well-developed amphidromy in the vicinity of the Solomon 

 Islands with its centre located at Nusosonga which has an amplitude of cm. 



In the north-east Pacific Ocean, the coast of the Gulf of Alaska, between 

 the eastern Aleutians up to Vancouver Islands, is a region with a relatively 

 constant phase of 240-270°, there is a crowding of co-tidal lines in the north 

 near the central Aleutians, and again north of Lower California. This dis- 

 tribution of the phase would fit an amphidromy with its centre south of the 

 Gulf of Alaska. The 60° lacking for a full revolution can be distributed be- 

 tween Lower California and the Hawaian Islands. For a further portion of 

 the eastern boundary of the Pacific Ocean Dietrich assumes two other am- 

 phidromies: one in front of the Gulf of Panama and another one in front 

 of Chile with its centre south of Easter Island. Both amphidromies are 

 indicated by phases and amplitudes observed at coastal localities, but their 

 position and form is uncertain in the open oceans due to lack of observations. 

 The few harmonic constants at present available for the central Pacific are 

 insufficient for an accurate drawing of co-tidal lines. The few constant of 

 places bordering this region seem to point to a rotation of the phase of 360° 

 to the left. The phase of several islands in this region would fit very well 

 in this picture. Dietrich assumes, therefore, a large amphidromy in the Central 

 Pacific with its centre north of the Samoa, Tahiti and Gambier Island. The 

 decrease in the amplitude of the semi-diurnal tides in the centre of the am- 

 phidromy would explain why the establishment and the differences in time 

 of the occurrence of high water in the Tahiti region (approximately between 

 140° and 160°W. and between 25° S. and the equator) show such an inextricable 

 confusion. 



Including another amphidromy in the Southern Pacific Ocean at about 

 50° S. which actually belongs to the belt girding the Antarctic between 70° 

 and 50° S. lat. Dietrich's map shows for the entire Pacific Ocean six amphi- 

 dromies and two pseudo-nodal lines. A comparison with v. Sterneck's pre- 

 sentation shows considerable differences both in the northern and in the 

 southern sections. The differences with Harris's map are still greater. Even 

 though the increased number of observations has eliminated many uncertain- 

 ties, Dietrich's map should still be regarded as provisional, and only more 

 observations will prove its reliability. 



5. The K x Tide as the Typical Tide Wave of the Diurnal Tides. (See Chart II) 



It is to be expected that the diurnal tides will show a simpler picture than 

 the semi-diurnal tides because of their longer period. This circumstance will 

 compensate for the disadvantage that there are fewer harmonic constants for 



