304 THE POPULAR SCIENCE MONTHLY. 



the parent glacier, the form of its bed, and the depth of the water 

 at its mouth. The larger fragments originate for the most part 

 along that remarkable break which is presented in the normal for- 

 mation of the coast-line between Egedesminde and the Svartenhuk 

 Peninsula. Rink enumerates not more than thirty Greenland gla- 

 ciers which discharge really large icebergs, and of this number 

 only six or eight yield blocks of the first magnitude. 



The average velocity of the congealed masses is about fifty 

 feet in the twenty-four hours, but in some places a much greater 

 speed has been recorded, though still varying considerably with 

 the seasons. A branch of the Augpadlartok glacier, north of 

 Upernavik, moves at the rate of one hundred feet a day, the high- 

 est yet measured. But how enormous must be the pressure of the 

 inland ice-fields to discharge into the sea the vast quantities of ice- 

 bergs which are yearly sent adrift along the Greenland seaboard ! 

 Estimated in a single block the annual discharge from each of the 

 five best-known glaciers would represent a mass of about seven- 

 teen billion cubic feet in capacity, and fifty-six hundred feet in 

 height, depth, and thickness. Reduced to a liquid state this mass 

 would be equivalent to a stream discharging seaward five hun- 

 dred cubic feet per second, or 15,500,000 a year. 



The formation of this drift ice, or floating icebergs, is one of 

 those phenomena which were discussed long before the seaboard 

 had been studied, or before the breaking away of the frozen masses 

 had actually been witnessed. "Wherever the glaciers discharge 

 through a broad valley preserving a uniform width and depth for 

 a considerable space, and advancing seaward through a fiord of 

 like dimensions, and with gently sloping bed, the ice may pro- 

 gress without any of those accidents caused by the inequalities of 

 more rugged channels. Under such conditions the compact mass 

 glides smoothly forward over its rocky bed without developing 

 any rents or fissures. But as it moves down like a ship on its 

 keel, it tends to rise, being at least one twentieth lighter than the 

 displaced water. It is also left without support by the sudden 

 fall of its bed beyond the normal coast-line. Nevertheless, it still 

 continues its onward movement through the waters to a point 

 where its weight prevails over its force of cohesion with the frozen 

 stream thrusting it forward. At this point it snaps off suddenly 

 with a tremendous crash, and the iceberg, enveloped in»a thousand 

 fragments projected into space, plunges into the abyss and whirls 

 round and round to find its center of gravity amid the troubled 

 waters. On recovering from the bewilderment caused by all 

 this tumult and chaos, the spectator finds that the glacier has 

 apparently receded a long way toward the head of the bay, in the 

 middle of which a crystal peak is seen slowly drifting away with 

 the current. . In this he recognizes the huge fragment detached 



