THE CLIMATOLOGY OF THE UNITED STATES. 33 



rents coining from southern latitudes, flowing in a north- 

 easterly and easterly course and striking the western 

 coasts with a temperature above that of the surrounding 

 water. 



The mild climate of the British Isles is attributed to 

 the influence of the gulf stream. There may be other 

 causes, but these currents certainly have a considerable 

 share in producing the effects which we notice. The gulf 

 stream flows northeasterly at some distance from our 

 coast, while a cold current from the Arctic regions passes 

 southward between the coast and the gulf stream, conse- 

 quently much of the influence of this latter stream is here 

 counteracted. In the Pacific, a great ocean current exists 

 similar to the gulf stream ; it is called the Kurosiwo or 

 Japan current, and flows from the coast of Japan in a 

 northeasterly course towards the Aleutian Islands and 

 Alaska, a small part passing into Behrings Sea and the 

 balance sweeping down the Pacific coast of the United 

 States. Owing to its great size, it preserves a very even 

 temperature throughout its long course, both in winter 

 and summer, and consequently has a marked influence 

 upon the climate, not only of Alaska but of British Co- 

 lumbia and the regions to the south, giving these places 

 very mild winters. Sitka, in the southern part of Alaska, 

 corresponds in latitude to the northern part of Labrador, 

 and yet its winter climate is not much colder than that of 

 New York. 



The average temperature of this current, as it reaches 

 San Francisco, is about fifty-five degrees, and as it tem- 

 pers the cold of winter it also mitigates the heat of sum- 

 mer ; but here another feature of this climate, the trade 

 wind as it is called, presents itself. This is in reality a 

 continual indraught of air from the ocean during the sum- 

 mer season, caused by the rising of the air in the great 



ESSEX INST. BULLETIN, VOL. XVIII. 4 



