DAILY VARIATION— SEPTEMBER TO MARCH. 



55 



The amplitude ol the daily oscillation increases steadily from iScptembcr to January and 

 decreases frLim January to Marcii, with tiie single exception of the month of December in 

 which it is somewhat smaller than in November and January. As December showed this 

 peculiarity each year it is probably a real effect. 



Before discussing the physical meaning of the curves for this period in McMurdo Sound, 

 it is desirable that we should compare the daily variation of temperature over the Barrier, 

 and also at other places of high latitudes. 



Daily Variation of Temperature on the Barrier. — The method of obtaining the daily variation 

 from temperature observations made during sledging journeys on the Barrier has been 

 described on page 21. 



By combining the observations made on the Barrier by different parties and dividing 

 the observations into months irrespective of the latitude in which they were made, the follow- 

 ing results have been obtained, from which it will be seen that the temperature amplitude 

 on the Barrier is much larger than in McMurdo Sound (table 20) : — 



Table 21. 

 Daily Variation af Temperature on the Barrier. 



The variations for each month have been plotted in figure 21, but the soale has had 

 to be reduced considerably from that used for figure 20, therefore the mean summer daily 

 variation for Cape Evans has been plotted on the same figure for comparison. 



For the three months November, December and January combined, the amplitude on 

 the Barrier was ir5°F., while for the same months in McMurdo Sound it was only 4-0°F. 

 A comparison of the simultaneous temperatures measured on the Barrier and at Cape Evans 

 is very instructive and gives a real insight into the cause of the large difference in the daily 



