112 MARION EXPEDITIOX TO DAVIS STRAIT AND BAFFIN BAY 



tion becomes focused on the proportions of the height to which a 

 berg towers above the sea, as compared with the depth to which it 

 extends beh)w the surface. Obviously, mass for mass, a pinnacled 

 berg will rise to a greater height above the water than a more uni- 

 form or blocky shaped one. In the majority of cases of icebergs, 

 therefore, calved from glaciers in the north, height tends to ap- 

 proach draft. Steenstrup, we find, gives 1:7.4 or 1 : 8.'2 for the 

 approximate proportions of a floating berg, height to draft; and a 

 square blocky berg as 1:7 to 1:9 of its mass. The figures offered 

 by Krummei (1907, p. 520) are 1:8 as cne extreme and 1:4 as the 

 other, with the common run equaling 1 : 5 to 1:6. 



There are several records of actual measurements made on ice 

 l)ergs as follows: The Denmark expedition observed a berg off the 

 east Greenland coast which measured 108 feet high and "270 fee', 

 draft, or proportions about 1 to ?). Dawson (1907) mentions meas- 

 uring an iceberg August 7, 1894, stranded in the Strait of Belle 

 Isle. It rose 105 feet above the sea in a depth of 342 feet of water, 

 or proportions of 1 to 3. Rodman (1890, p. 7), describes a tall, 

 spired berg 100 feet in altitude that was grounded in IG fathom.s 

 of water in the Strait of Belle Isle: proportions almost 1 to 1. 

 The international ice patrol (Smith. 1925, p. 81) measured a berg 

 east of Xewfoundland by sextant angle as 106 feet, and its draft 

 by means of a wire drag was 200 feet; proportions 1 to 2. The fol- 

 lowing table of approximate i)rop()rtions (height to draft) for bergs 

 south of Newfoundland has been compiled with consideration for 

 density values and also the results of actual measurements of bergs of 

 various shapes. 



TvTX-' : rroportions (exposed to submerged) 

 Blocky. preeii)it(;U8 sides 1 : ~) 



Komided 1 : 4 



I'icturesiiue, Greenland 1 : 3 



Pinnacled and ridged 1:2 



Last stages, horned and winged 1:1 



It is seen that the (xreenland bergs, characteristically pinnacled 

 and domed, have a much smaller draft than has heretofore been the 

 connnon impression. It is not surprising, therefore, that sizeable 

 bergs can drift in relatively shallow waters, as over the Grand Bank] 

 or across the sill of Davis Strait. 



DiSIXTEGHATION AND MeLTING OF ICEBERGS 



As soon as an iceberg cleaves from the glacier front and is water 

 borne, the processes of wastage ronnnence. This phenomenon pro- 

 ceeds in the following three ways: (1) Melting, (2) erosion,"" and* 

 (3) calving. 



It is seldom, under actual conditions met at sea, that all three 

 methods of disintegration are not at work, but one type is oftem 

 more active than the other two until a change of the sea or a changei 

 in the shape of the ice causes a rearrangement of the three agencies. 



*" The word "erosion " is used here to designate the accelerated rate of meUinj? thati 

 takes place when icebergs are washed by waves, by swell, or by rain. Any motion which i 

 carries away the water which is in contact willi the ice and brings a fresli supply of: 

 warmer water to the ice surface materially liastens molting. Erosion, then, as used, re- 

 fers not only to the fi'icrioiial action of tlie water lint it also includes the f.ir greateri 

 melting eflVct. 



