134 MARIOX EXPEDITION TO DAVIS STRAIT AND BAFFIX BAY 



miles per clay with a wind force of 4 to 5. There is, however, one 

 modifyino; factor, namely, the deep draft of the ice, 500 to GOO feet, i 

 which exceeds the depth "of the wind current. The bottom portion of 

 the body drag;<iino- in tlie deep, dead water will, therefore, retard 

 the ice probably as much as '20 per cent. In the case of the bulky 

 and boxlike type of ber<>: it will reduce the drift to 2 and :5 miles 

 per day for 4 to 5 and G to 7 winds, respectively, but the smaller- 

 wintjed and ]>innacled berirs float entirely in the wind current and | 

 develop no dra<j: whatsoever. f 



Now, combinin«r (a) and (h) {p. Vy4), we arrive at a resultant 

 drift which for the deeper-draft type of ber<is is 40° to the right of 



Wind Effect on the Drift of large icebergs 



Figure s8. — In Uie case of a wind with a velocity of 4-5 

 Beaufort scale, the berg will drift 40° to the right of 

 the wind (in the Northern Hemisphere), at the rate ot 

 2.8 miles per day ; line A in this figure. In the case ot 

 a wind velocity of 6-7 Beaufort scale, the berg will drift 

 40° to the right of the wind at the rate 'of 4.:! miles per y_ 



day : line B. 



the wind. Column A represents the drift that the wind would im 

 part to the berg if it did not affect the water and column B represent' 

 the mean f rictional current for winds of the given strength. We havei 



Wind strength 



Beaufort 4-5- 

 Beaufort 6-7. 



A B 



KesultanI 

 Direct J Frictional ; drift' 

 force 1 I current ' I 



1.6 

 2.5 



1 Miles per day. 



In the case of the lighter draft bergs, i. e.. those of i)n)i)()rti.)ns 2: 

 and 1 : 1, drift 54° to the right of the wind as follows : 



Wind strength 



Beaufort 4-5- 

 Beaufort 6-7 - 



Direct 

 force ' 



5.5 

 8.5 



Frictional 

 current ' 



2.5 

 3.7 



Resultant 

 drift > 



1 Miles per day. 



