CEUISE OF STEAMER CORWIN IN THE ARCTIC OCEAN. 127 



These currents, caused by the trade winds, run in a westerly direction until turned in the direc- 

 tion of the meridian by contact with the eastern coasts of the great continents. In the case of 

 the Atlantic current the new direction is to the northward, owing to the direction of the coast 

 line upon which it impinges, while the Pacific current is divided, one portion going southward 

 and one northward, the latter being the current now under consideration, a small portion of 

 which I believe passes through Bering Strait, but in a modified form, both as to velocity and 

 temperature. 



Referring again to the causes of the difference in the specific gravity of sea water in different 

 parts of the ocean, the temperature and percentage of salt, we find that the former decreases and 

 the latter increases it ; and, as in the case of two strata of different specific gravity coming in 

 contact, the stratum having the greater would, in obedience to the laws of gravitation, sink below 

 the other, it will be seen that an equatorial current can exist as a surface current only so long as 

 its temperature is sufficiently high to render it lighter than the adjoining stratum. As it comes 

 in contact with the colder waters in its passage its temperature falls and it sinks below the waters 

 of the higher latitudes, which, on account of decreased evaporation and the larger amount of 

 fresh water discharged into it from streams of melted snow and ice, contains much less salt, after 

 which it may continue its course as an under current until neutralized by the surrounding water; 

 or, as in the case of a water like Bering Sea, the result of a contact between two currents must 

 be the creation of a single current, whose direction will be that of the stronger of the originals, 

 and whose velocity, temperature, and specific gravity will be their mean. 



A branch of the Kuro Siwo, thus modified, would have a temperature but little above the 

 normal temperature for that latitude. Its velocity would also be so much reduced that it would 

 be readily influenced by winds, retarded or wholly stopped by northerly winds, and accelerated 

 by winds' from the south, and also subject to modification by the ever-changing position of the 

 ice-pack. 



ARCTIC ICE NOTES. 



The great impenetrable mass of ice which, so far as has been observed by man, surrounds the 

 polar regions, is called the "pack." The loose ice or detached pieces which float near the edge of 

 the pack, and, under certain conditions of wind and current, become a part of it, is called "drift- 

 ice," and is designated "patch, "floe," or "field," according to its magnitude, ranging from the 

 smallest pieces to several miles in extent. Icebergs are formed from glaciers, and although found 

 floating on the sea are entirely foreign, to it. The glacier, being formed on land above the sea 

 level, descends, in obedience to the laws of gravitation, until it meets the sea, where large pieces 

 called "bergs" are detached. The. large, high floes of sea ice, which in size resemble the smaller 

 bergs, were appropriately named "floebergs" by Captain Fielding, of the Royal Navy, a member 

 of the Nares Expedition. 



Sea ice forms at a temperature of 28°.5 F., and at first retains a portion of the salt and other 

 impurities. When its temperature is low sea ice is brittle, but under a higher temperature it 

 becomes tough and flexible. Successive changes of its condition in this respect eliminate the salt, 

 so that in time it becomes pure, and resembles glacier ice. At times it is difficult to distinguish 

 one from the other. Sea ice, when first formed, is opaque, and is white or grayish in color, accord- 

 ing to the condition of the water. If near the shore, or in shallow water, the latter color prevails. 

 As the process of purifying itself goes on it becomes green, and later (when the salt and other 

 impurities are almost entirely eliminated) it shows a clear deep blue. It is no unusual thing to 

 see these different colors in the same floeberg, caused by the action of the currents pressing layers 

 of ice of different ages one over the other. As these colors are bright and distinct the effects in 

 the clear sunlight are often very beautiful. There are also occasional small yellow patches on 

 the surface of the ice, due to the presence of microscopic animalcula. The thickness of the ice 

 in the Polar Sea is variously estimated. The specific gravity of sea ice is less than .9, and if the 

 floebergs were regular in form, by measuring the height above water, the depth might be ascer- 

 tained by a simple calculation. But the irregularities of their form render this impossible; conse- 

 quently these estimates vary greatly. Dr. Hayes mentions seeing ice 100 feet thick in Smith's 

 Sound. Scoresby speaks of ice in the vicinity of Spitzbergen 20 feet in thickness. Parry, when 



