124 MARIOX EXPEDITIOX TO DAVIS STUAIT AND BAFFIN BAY 



first explosion occurred during a dense fog which sliut off all view, 

 but repeated heavy calvings were heard from time to time following 

 the blast. Another mine suspended from one side to a deptli of 10 

 feet brought down much loose ice. but a second charge placed at 20 

 feet below the surface of the water jarred the berg most of all. The 

 last mine, being against the side wall of the berg at a depth of 80 feet, 

 detached great cpiantities of ice, causing the berg to rise and then fall 

 sideways and to break s(iuarely in two at the point where the mine 

 had been placed.*'^ Gunfire has no material effect, but only shakes 

 ;lown a few tons of ice from the point of impact. 



The Effect of Explosives on icebergs 



FiGiKE 83. — On .Tune 5. 192;{, the IT. S. Coast (iuanl cutter Modoc cxploiled four 

 yO-pound gun e'otton mines suspended from this l)er<>- at a depth of 00 feet. The 

 berg was observed t'> quiver perceptibly the instant of tlie explosion, and several 

 growlers were detached from the niaiii liudy. hut no other residts were observed 

 nor did the berg change in equililiriuin. (Ofiicial photograph, international ice 

 patrol.) 



The melting of icebergs induces a circulation of the water in which 

 they float. Pettersson (1904, p. 286) and Saiidstrom (191.-). p. 245) 

 found l)y laboratory experiments that fresh ice melting in a tank 

 of salt water tends to induce three currents: (1) A cold surface cur- 

 rent of low salinity away from the ice; (2) an intermediate current 

 of relatively warm salty water toward the ice; and (H) a cold cur- 

 rent sinking diagonally away from the ice. Pettersson in several pub- 

 lications has offered these experiments as an exi)lanation for many 

 (»f the circulatory features of the world's oceans. Barnes (1910) as 

 a result of ice investigations in the St. Lawrence River believes that 

 the detection of such movements around bergs by means of precise 



'•' Zeusler (1025, p. 41) gives a good description of mining operations as occasionally 

 carried out by the ice patrol. 



