282 G. F. McEwen. 



of fogs in the region south of San Francisco and also in the region 

 north of there, so we have the necessary data for testing the above 

 conclusion. The fog curves (Figs. 8, 9, 10, and 11) representing this 

 data have heen drawn in connection with the corresponding curves 

 showing the temperature differences. The resulting similarity of the 

 fog curves and the corresponding temperature curves is just what would 

 be expected from the above assumption regarding the way in which 

 the fogs are formed. 



An extensive investigation of the influence of ocean temperatures 

 and local winds on climate has been carried on by many meteorolo- 

 gists since the publication in 1817 of Humboldt's chart of The Iso- 

 thermal Lines of the Earth, and it was suggested by Richter (5) in 

 1887, that a knowledge of the isothermal lines of the ooean along the 

 coast would probably explain the formation of our barometric maxima 

 and minima, and afford a basis for the calculations of meteorologists, 

 and for more accurate weather predictions than would otherwise be 

 possible. 



IX. Summary and conclusions. 



Numerous observations extending over a long period have estab- 

 lished the presence of abnormally cold surface water contiguous to 

 the west coast of North America, but a diversity of conflicting theo- 

 ries have been proposed by various writers to account for the phe- 

 nomenon. 



The conclusions reached by different investigators may be summa- 

 rised as follows. 



1. A cold arctic current flows south along the coast from the 

 polar regions. 



2. The Japan Current, because of its passage thru high latitudes, 

 becomes cooled, and as it flows south along the coast of the United 

 States, appears as a cold stream because its temperature corresponds 

 to the normal value prevailing in higher latitudes 



3. The accumulation of water in the south polar region causes an 

 excess of pressure which drives the cold bottom water northward with 

 an increasing velocity owing to the diminishing distance across the 

 Pacific, till when it reaches the latitude of Sitka, Alaska, owing to 

 the deflecting force due to the earth's rotation it is driven up the 

 continental slope and. flows south as a cold current, since it has no 

 other outlet. 



