892 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



of the sun overcomes their hold to the main ice belt, and they fall 

 at once into the sea and make a freshet, which breaks the Avay 

 throuo-h Baffin's bay and East Greenland sea, and they then float 

 out to the Atlantic. The berg must fall into Avater deep enough 

 to float it. The moment it touches ground its voyage to the 

 Atlantic is over. If there is no fall of ice bergs the channels 

 throuoh the Polar sea do not open for that summer. Capt. Ross 

 had to summer over tAvo years in his second voyage to the Pole, 

 in 1830, because the upper water of Baffin's bay did not open by 

 this iceberg freshet. 



Captain Scoresby and other Arctic navigators, speak of seeing 

 five hundred icebergs at one time. Suppose they contain one 

 hundred cubic miles of ice; the}'- would, by their sudden fall, 

 raise the Avater of the polar sea two feet, and that would make 

 freshet enough to open the channel to the Atlantic. Had Ave no 

 other data, tlie phenomena of the icebergs are sufficient to warrant 

 the supposition of an open polar sea. If there was no open polar 

 sea, there coidd be no icebergs, as the Avater floAving into Behring's 

 straits Avould floAV along the outer edge of this central glacier, and 

 minoflins: Avith the rivers flowiuir north, would melt the outer eds^o 

 of this central glacier gradually aAvay, and ahvays keep it AA'ithin 

 certain limits. In fact, this fresh Avater flow is the channel in 

 which vessels have sailed along the Arctic coasts. 



Icebergs always float in fresh AA^ater, as they melt away fast 

 enough to kept themseh^es in a bath of fresh Avater at 35° F. 



All the Arctic navigators speak of meeting icebergs in their 

 voyages to higher latitudes. Where there is no open passage, of 

 course there are no icebergs, for there w^as no fall of icebergs to 

 open the passage. The fall of 100 cubic miles of ice would raise 

 the temperature of the polar sea about 5° F. A cubic mile of 

 Avater Aveighs one million million pounds. 



ToAvards the south pole icebergs are rarely seen, as there there 

 is a central glacier, and the ice melts aAvay at the outer edge, 

 except occasionally it may overhang enough to make a regular 

 iceberg by falling oft'. 



Ice sinks l)y Ijeing drilled, so to speak, by w^ater at 40° F con- 

 stantly sinking into numerous holes in the ice. As soon as this 

 Avater is cooled to 32°, it is displaced by new Avater at 40°. The 

 ice ))y this process becomes like a great mass of candle molds. 

 Here is an artificial iceberg, about six inches cubical diameter, 

 made of one-half inch glass tubes six inches long, all of them 



