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THE POPULAR SCIENCE MONTHLY 



shading (Fig. 4). The region occupied by the first comprises a tri- 

 angular body of water covering the greater jDortion of the North Pacific 

 Ocean, and also a trapezoidal body extending in a southeasterly direc- 

 tion to the coast of Chile. The nodal line near Acapulco, Mexico, is 



very apparent from' observation, as can be seen upon consulting the 

 chart of cotidal lines for the Pacific Ocean (Fig. 7). The same chart 

 shows the stationary character of the oscillation by the fact that at the 

 three angles of this huge triangle — that is, in Panama Bay, the Gulf 



