Tides of the Oceans 483 



with a minimum of amplitude (Rio Grande do Sul only 5 cm), indicates 

 a pseudo-nodal line. North thereof the variations in phase are small with 

 large tidal ranges up to Cape Sao Rogue and even farther along the entire 

 north-east coast of South America (disregarding the wide shelf of this coast). 

 This distribution along the coast becomes less definite towards the open 

 South Atlantic Ocean, so that the distinct nodal line on the coast (according 

 to the observations on the islands) changes into a gradual variation of the 

 phase, which becomes more pronounced in a north-eastern direction towards 

 the African coast. While the increase in the phase is gradual, the amplitudes 

 remain constant between 40 and 50 cm; only in the inner part of the Gulf of 

 Guinea they increase to 75 cm after crossing a wide shelf. 



North of the equator there seems to exist an antinode which extends 

 over the entire width of the ocean from Pernambuco to West Africa. This 

 anti-node is joined northward by a well-developed pseudo-nodal line. The 

 increase in phase in the western part between Martinique and Puerto Rico 

 is 165° and the phase in the eastern part between Cape Verde and the Tropic 

 of Cancer vary by the same amount. In the west the crowding of co-tidal 

 lines seems to originate from an amphidromy, whose centre is located in 

 the eastern part of the Caribbean (Ponce on Puerto Rico where amplitude 

 of M 2 = 1 cm). In the western part of the Atlantic, north of this nodal line 

 up to the south coast of New Foundland the phase varies but little and de- 

 creases slightly. At the coast of the eastern N. Atlantic, on the contrary, 

 the phases increase continuously from N.W. Africa, to the Canary Islands, 

 Madeira, the Azores and farther along the European coast, so that this entire 

 northern section of the North Atlantic Ocean is occupied by a very well- 

 developed amphidromy. 



The transition to the European North Sea takes place by a well-developed 

 nodal line in the Denmark Strait and by a narrow amphidromy with a sudden 

 change in phase of 150° over a short distance between the Hebrides and the 

 Shetland Islands in the east and a corresponding decrease in the phase on 

 the east coast of Iceland. The centre should lie north-west of the Faeroe 

 Islands where the amplitude is only 10 cm against a minimum of 33-5 cm 

 on the east coast of Iceland and 395 cm on the Shetland Islands. 



The tidal picture of the Atlantic Ocean is clearly shown by the co-tidal 

 lines on Chart I, and will not be changed essentially by new observations. 

 This is proven by the fact that the presentation of the Atlantic Tides (see 

 Fig. 203) given by Sterneck (1920) does not deviate essentially from Dietrich's 

 newer map. The divergence from Harris's map is, however very great. Harris 

 assumed a very remarkable pattern of the co-tidal lines, particularly in the 

 region of the Northern Atlantic Ocean; but he had already found the am- 

 phidromy in the North Atlantic. 

 (b) Indian Ocean (Table 81 J 



Dietrich points out as a particular feature in the Indian Ocean the very 



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