60 GENERAL, REMARKS. 



After the month of May, heavy bodies of northern or Arctic ice 

 are seen moving to the southward every year, sometimes as late as 

 the end of August. It is variable in quantity and breadth, but forms 

 a constant obstruction from Indian tickle, on the coast of Labrador, 

 to the Fogo islands. The stream generally breaks in July. 



The bergs which follow the slob and field ice are detached por- 

 tions of the true polar ice, which is formed upon the land, and car- 

 ried down to the sea by glacial action. The glaciers perform for 

 these frigid regions the same function as that performed by the rivers 

 of the temperate latitudes by serving to distribute the excess precipi- 

 tation. From the frozen interior of the Arctic continent these rivers 

 of ice make their way through valley and gorge to the shores of 

 the ocean, and even beyond; the face of the glacier being thrust 

 forward into the sea by the enormous pressure in the rear until the 

 buoyant effect of the water upon the submerged portion is sufficient 

 to detach it from the main body, and the huge fragment becomes 

 a floating island or mountain of ice, which is borne away by the 

 prevailing currents. 



The thawing process alone, occasioned by the increased tempera- 

 ture of air and water during the polar summer, would scarcely suf- 

 fice to reduce these enormous masses of ice to the size usually ob- 

 served. Their disintegration is brought about ordinarily from within. 

 Even in its original condition the surface of the glacier ice is wrinkled 

 with chasm and crevasse, penetrating more or less deeply into its 

 interior. The deepest of these depressions collect the water due to 

 the melting of the upper part of the berg until they overflow ; a fall 

 in temperature occurs, the surface of this water, and later its entire 

 volume, is converted into ice, and hj the tremendous expansive force 

 of this change the mass of the berg is shattered. 



Once beyond the limits of the polar regions, the process of dissolu- 

 tion is rapid. The berg, alwa^^s heated upon its southern side, is in 

 unstable equilibrium, and by reason of its frequent topplings, con- 

 stantly exposes a new surface to the action of the sun's rays. Under 

 these conditions its ultimate annihilation is a matter of a compara- 

 tively short time. 



The icebergs seen off the Great bank are of such extent and occur in 

 such numbers as to constitute, with their attendant fogs, the most 

 dangerous of all the obstacles with which the navigator of the North 

 Atlantic has to contend. Their frequency in different years varies 

 in a wholly inexplicable manner, certain seasons being notable for 

 their extraordinary abundance, while in others the number observed 

 is far below the average. June is the month during which they are 

 most numerous along the transatlantic route. 



The phenomena of the drifting of the bergs to the limits mentioned 

 above have been attributed to the warm waters of the Gulf stream 



