DIRECTION. 



Ill 



We are chiefly concerned witli blizzard winds, we will therefore examine first the effect 

 of the land distribution on these winds. If there had been a large number of observers 

 taking simultaneous observatio)is at many different points it would have been possible to 

 show the actual motion of the air at any given time during a blizzard. As these observers 

 were not present the next best thing is to examine observations taken at different times in 

 different places during blizzards. This it is possible to do from the meteorological records 

 kept by the various sledging parties. Also the directions of the sastrugi give valuable inform- 

 ation as to the directon of high winds. 



Strenm Lines during Blizzards. — In figure 37 the results of such an iuvestio-ation are 

 shown. The stream lines indicated on the diagram are what one would expect from the con- 

 figuration of the land, but in support the following evidence for several of the mo.st 

 important positions is added. 



Position A. — -Cape Evans. — Wind E.S.E. During blizzards the wind was constantly from 

 S.E., E.S.E. and E., of these E.S.E. was the most frequent asid this direction is shown. 



Position B. — ^The prevailing winds over McMurdo Sound were clearlv indicated by the 

 direction of the sastrugi. There were two distinct sets of sastrugi on the line joinin" Cape 

 Evans and Butter Point. One set. the most marked, indicated a wind from somewhat south 

 of east and the other set a wind from between S.E. and S.S.E. There can be little doubt 

 that the former were formed during the violent winds which were deflected by the shoulder 

 of Erebus ; while the latter were formed bv tlie moderate south-easterly winds which 

 constantly blew through McMurdo Sound from the Barrier. Both sets of sastrugi became more 

 southerly as the Sound was crossed from east to west ; the actual observations were : 



Table 63. 

 Sastrugi in McMurdo Sound. 



Position C.—Hut Point.—Wind E. to N.E. Both tlie records ni the Discovery Expedition 

 and of the men of our expedition who remained at Hut Point show winds between E. and 

 N.E. during the most violent blizzards. There can be little doubt that the wind is here 

 deflected by the high ridge running N.N.E. fi'ora Hut Point. 



Position Z).— Wind S.E. On March 12, 13 and U, 1911, a part.y was at the point 

 marked D during a very violent blizzard. S.E. winds were recorded throughout. 



Position £.— Variable winds. On July 4, 1911, the Cape Crozier party was at the point 

 indicated by E. Throughout this day an east-south-easterly blizzard blew at Cape Evans 

 with velocities up to 5'2 miles an hour, but the party recorded : 



' Overcast all day with steadily falling snow. Wind 3 to 4 with occasional gusts 

 from E.N.E. to S.E. and light breeze from S.S.E.' 

 thus showing variable winds during a blizzard which was giving steady high winds from the 

 E.S.E. at Cape Evans. 



Further within the large bay in the south of Ross Island the wind is always light and 

 variable. The bay was explored right up to the coast by members of Captain Scott's 

 first expedition and it was found to be full of light snow showing little or no signs of heavy 

 winds. Dr. Wilson called this bay Tranquil Bay. 



