B. TERRESTRIAL PHYSICS AND METEOROLOGY. 67 



Iceland, at a depth of 200 to 300 fathoms, water was met 

 with of 32 Fahr., while in the neighboring portion of the 

 Atlantic Ocean the temperature at the same depth was 

 above 46.4. 



The general variation of the surface temperature amounts 

 to 9 Fahr., or even more, but becomes less as we descend, 

 the decline, however, not being every where in the same ra- 

 tio. Deep-sea strata reach their maxima and minima a little 

 later than the surface layer. 17 C, October 1872, 315. 



UNVARYING COURSE OF CIRRUS CLOUDS. 



It seems to be generally admitted that there are two cold 

 poles (points of minimum temperature) in the northern hem- 

 isphere, one in Asia, and the other in North America, and 

 that from these the trade-winds radiate, regulating, as they 

 veer to one side or the other, the changes of the weather. 

 To complete the statement, attention is called to the fact 

 that it is extremely probable that the high cirrus clouds are 

 unaffected by the variation in course, between northwest 

 and southeast, which the trade-winds experience on the east- 

 ern borders of the two great continents, but preserve the 

 normal direction imparted to them by the rotation of the 

 earth namely, that of the anti-trades and, at a great ele- 

 vation, continue undisturbed from west or west-southwest 

 to east-northeast. Observations are not complete enough 

 to establish the latter proposition, but numerous concordant 

 statements render it so probable that it seems worthy of 

 the attention of local and other observers. 



In North America, where the axis around which the wind 

 veers lies decidedly between northwest and southeast, as in 

 Eastern Asia, the fact seems better substantiated than in 

 Europe (can, indeed, be considered as fixed), and the infer- 

 ence is justifiable that the condition on the eastern coast of 

 Asia is similar. Russell verifies by his own observations in 

 Canada, in Washington, in the Southern States, and Cuba, 

 the statement of Espy, that in the United States there is an 

 unvarying upper current of air from the west. Blodgett as- 

 serts that at Philadelphia, at all seasons, a western current 

 can, not unfrequently, be detected by cirrus clouds. In 

 Northern Asia, even on the east coast, no exact information 

 on this point has been supplied, on account of the neglect to 



