480 



At the "Discovery's" Winter Quarters the highest mean pressure occurred in the autumn and the 

 lowest in the spring, the means for the four seasons showing a very uniform progression from one to the 

 other. At the " Gauss," the moan pressure was throughout lower than at the " Discovery," but higher in 

 the summer than in either of the other seasons, the seasonal march of pressure being with this exception 



opt-mg_ 



Summer 



Aubumn 



Winter 



29-0 



29-0 



Fig. 1. Mean pressure for the four seasons. 



similar to that at the " Discovery's " position. During the drift of the " Belgica," the highest mean 

 pressure occurred in the winter and the lowest in the autumn, the mean in spring and summer being 

 alike; the yearly march of pressure recorded was therefore very unlike that experienced at the other 

 stations. 



Only 11 months' observations are available for Cape Adare. The lowest mean pressure was reached 

 there in the spring and the highest in the summer, the seasonal change being very similar to that 

 experienced on board the " Gauss." 



DIURNAL OSCILLATION OF PRESSURE AT WINTER QUARTERS. 



The hourly means have also been combined for each of the four seasons in order to ascertain whether 

 they exhibited a diurnal variation of pressure. 



For this purpose mean values were computed for the initial as well as for the final midnights, and the 

 difference between the two distributed proportionately over the day in order to eliminate the non-periodic 

 variation. This was done by pivoting the correction, so to speak, upon the noon value, and applying to 

 the initial and terminal values one-half of the difference between them, subtracting it from the higher of the 

 two and adding it to the lower, the intermediate hourly values receiving a proportional amount of the 

 difference, and the noon value, of course, remaining unchanged. The results are shown in fig. 2, 



