THE TIDES 537 



of Alaska and off the coast of Luzon — the tide occurs at nearly one 

 and the same time, while the amount of rise and fall is considerable. 

 Also, that for a considerable area around each of these angles, the time 

 of tide changes slowly in going from place to place. The range of tide 

 gradually decreases from the Gulf of Alaska, where it is about eight 

 feet, to the western groups of the Aleutian Islands — the range off Eat 

 Islands being less than two feet. 



The South Pacific system embraces an L-shaped region extending 

 from the coast of California and Lower California to the shoals and 

 islands north of New Zealand, thence southeasterly to southern Chile 

 and Grahani Land. 



Three no-tide points occur in mid-ocean, one occurs in Norton 

 Sound, Alaska, one near either end of the Sea of Japan, and one in the 

 Gulf of Pechili. 



Tides at the Isthmus of Panama and Elsewhere 



Keferring now to the cotidal maps of the world, it appears that the 

 mean range of tide at Panama is 12.6 feet, while at Colon, just across 

 the isthmus, it is only 0.6 foot. That a great difference between the 

 tides at these two points exists was mentioned by Oviedo y Valdez as 

 long ago as 1526, and the question as to the reasons therefor has been 

 frequently raised even up to the present time. Upon consulting the 

 small chart of the world, it will be seen that Panama is situated at one 

 angle of the triangular area where the rise and fall would naturally be 

 greatest. 



On the other hand, the tides which enter the Caribbean Sea from 

 the ocean must be small because of the proximity of the nodal line set- 

 ting out from the Lesser Antilles (Fig. 4). The time and range of the 

 small tide at Colon indicate that it belongs to the equilibrium tides of 

 the Caribbean Sea itself. 



Likewise the small tides in the southwestern portion of the Gulf of 

 Mexico are equilibrium tides belonging to the gulf. 



The tides in the eastern portion of the Mediterranean are equilib- 

 rium tides of that body. 



The tides in the Eed Sea consist partly of a bodily oscillation of that 

 sea and partly of a progressive wave from the Indian Ocean. 



The tides found along the South American coast, from Cape Horn 

 to Eio de la Plata, are derived from the tides of the Pacific Ocean, as 

 is apparent from the chart of cotidal lines for the Atlantic Ocean. 

 The range of tide is about thirty feet at the eastern end of Magellan 

 Strait and less than two feet at Buenos Aires. 



Dependent Stationary Wave 



It has already been noted that a dependent stationary wave occupies 

 the Bay of Bengal. Such waves are found in the following arms of the 



VOL. LXIIV. — 35. 



