§ 501-506. THE CLOUD REGION, ETC. 271 



Stormy latitudes are between tlie parallels of 55° and 60°, the most 

 foggy between 50° and 55°. 



50-i. How suggestively do these two groups of phenomena re- 

 influences of tiie Gulf mind US, ou the oue hand, of the Gulf Stream and 

 bSi 'Currents 'Tf ^he ice-beariug currents of the north, and, on the 

 the south. other, of Cape Horn and the antarctic icebergs 



which cluster off the Falkland Islands!^ 



505. Sea fogs within 20° on either side of the equator are things 

 Sea fogs rare within of rare occurrcncc. Within this distance, however, 



20° of the equator— t • t t n n -. 



red fogs. on the north side, red logs of '' sea-dust (§ 822) are 



not unfrequently encountered by navigators. These can scarcely 

 be considered as coming within the category of sea fogs. The 

 falling of this dust in the form of fog is no doubt owing to those 

 influences (§ 881), the effects of which are so often observable 

 morning and evening in the settling smoke from neighboring 

 chimneys. The fogs which at early dawn are discovered hover- 

 ing over our cities or skirting the base of the hills, are of the same 

 sort. These particles of dust, like the atoms of smoke, are brought 

 into conditions favorable for radiation on occasions when the air 

 in which they are floating happens to have a high dew point. 

 Thus each one of these innumerable little atoms of smoke and 

 microscopic particles of sea-dust become loaded with dew, and be- 

 ing made visible, have the appearance of fog. Eed fogs, there- 

 fore, do not properly come under our classification of sea fogs. 



506. On the polar side of 40° at sea the weather is for the most 

 Cloudless regions and V^^^ cloudy. Ou the cquatorlal side, and espe- 

 heightofcioudsatsea. ^^^^^ ^'^^-^ ^^^ tradc-wlud rcglou, it is for the 



most part clear until we approach the cloud-ring, where clouds 

 again indicate the normal state of the sky at sea. What is the 

 height of the cloud region at sea? for vapor j^;?a?2e it can scarce 

 be called. As yet our sailor observers have not turned their at- 

 tention either to the height or the velocity of clouds. It is to be 



* Captain Chadwick reports, by letter of 30th April, 18G0, an iceberg, first seen by 

 him 14th September, 1859, in S. lat. 52° 25', long. 57° 8' W. ; next, October 10th, 

 in 47° 15' S., 59° 30' W., by the Wild Pigeon. Five days later he feU in with it in 

 lat. 45° 40', long. 58° 40'. It was last seen 7th November, in lat. 43° 44' S., long. 

 57° 14' W., by the British ship "City of Candy." Whether this were the same 

 "berg" or not, it shows that icebergs are not unknown to the north of the Falkland 

 Islands, as, indeed, the aqueous isotherm of 60°, Plate IV., indicates by its sharp 

 curve about those islands. 



