TIME— WEATHER. 11 



times according to this practice. Local time at Cape Evans is fifty-four minutes behind that 

 of the 180th meridian, hence for moat meteorological purposes, when local time is required, 

 it is sufficient to deduct one hour from the times given. As four minutes is imperceptible 

 on most of the meteorological self-recording instruments used, the clocks were set to station 

 time and hourly values tabulated. Conversion to local time was then obtained by deducting 

 one from the denominator of the hours at the head of each column. 



Cafe Adare and FramJieim. — ^Local time only was used at these stations. 



Weather. 



It will probably be useful to conclude this introductory chapter with a short general 

 description of the weather conditions which we are about to discuss in detail. 



Weather at Cape Evans. — McMurdo Sound is situated between two masses of high land : 

 Ross Island on the east and the Western Mountains on the west. The air motion in the 

 Sound is therefore limited, and all the winds can be classed according to whether the air 

 motion is through the Sound from the north or through the Sound from the south. The 

 former includes at Cape Evans all winds between E.N.E. and W., and the latter all winds 

 between W.S.W. and E., and these two classes will throughout be specified as northerly 

 winds and southerly winds respectively. There is a close relationship between the wind direc- 

 tion and weather, and it is convenient to consider the weather at Cape Evans under three 

 headings : — 



(a) The weather associated with northerly winds. 



(b) The weather associated with calms and light winds. 



(c) The weather associated with southerly winds. 



The period during which the wind blows with a greater velocity than 10 miles an houi 

 from the north and the south is 8 per cent, and 49 per cent, respectively ; while during 

 the remaining 43 per cent, of the time the air is calm or the wind velocity less than 10 

 miles an hour. 



Weather associated with Northerly Winds. — The chief characteristics of the type of weather 

 associated with northerly winds are relatively high temperatures and an almost total absence 

 of cloud. The air is nearly always clear during a northerly wind ; but the mnd sometimes 

 raises a little surface drift from the ground if there happens to be newly-fallen snow lying. 

 Northerly winds interfere very little with the outdoor work of the expedition and therefore 

 they receive very scant notice in the popular descriptions of Antarctic life, but we shall 

 see that they are very important from the meteorological point of view. 



Weather associated with Calms and Light Winds.— One of the interesting features of the 

 air motion in McMurdo Sound and on the Barrier is the tendency of the wind to bo either 

 entirely absent or to be blowing a gale. The records for twenty months show that the 

 wind was blowing at 30 miles an hour or over during 30 per cent, of the total period, 

 while during 22 per cen'. the velocity was 4 miles an hour or less. As far as I have 

 been able to find there is no other place in the world at which such a large proportion 

 of high winds is associated with such a large proportion of calms. In the summer the tem- 

 perature during calm weather is little different from the average of the month, but during 

 the winter it is very much lower. Except for its low temperature during the winter, calm 

 weather has no outstanding peculiarities : the sky may be completely overcast or completely 

 clear, and also occasionally snow falls. 



Weather associated with Southerly Winds. — During practically half the whole time the wind 

 blows from the south with a greater velocity than 10 miles an hour, and of this period a 



