VOYAGES OF ICEBERGS 131 



facilitated by the action of the prevaihng winds, which, in 

 this region, in the spring and summer, often blow with great 

 energy from the northwest. A berg one hundred feet high 

 and a mile long spreads a vast surface to these winds, and is 

 slowly but effectually impelled by them in the manner of a 

 sailing ship. 



From the time the berg is launched into the sea it is con- 

 stantly wasting ; unlike the lloc-ice, which receives important 

 accessions in freezing weather, the berg, on account of its 

 depth, whicli brings the greater part of the mass into water 

 above the freezing-point, steadfastly diminishes in volume; 

 the little ice-sheet which may form around the water-line 

 does not affect the size of the mass, yet this process of melt- 

 ino- goes on but slowly. In the first part of its journey it is 

 always in water which is at about the freezing-point. Most 

 persons are familiar with the fact that cakes of ice will float 

 for a long time in very cold water, and can thus imagine that 

 icebergs may journey a long way in the Arctic seas with but 

 little loss in bulk. It is when they come in contact with 

 the waters of the Gulf Stream that the dissolving process 

 beoins to go on in a rapid manner. The under-running cold 

 current, which moves southward toward the central parts of 

 the Atlantic, seizing on the great surface of the bergs which 

 extends downward — it may be to one or two thousand feet 

 below the surface — urges these masses of ice against the rela- 

 tively shallow and slow-running warmer tide. As they go 

 to the south the energy of the imjiclling stream constantly 

 diminishes, for the reason that the flow from the Arctic, no 

 lono-er confined within the channel between Greenland and 

 the mainland of North America, slackens, while with each 

 stage of the movement of the bergs toward the equator the 



