172 



PRESSURE. 



April May June July Aug. Sep. Oct. Nov. Dec. Jan. Feb. March April May June July Aug 



Fig. 37. Pressure cUffeiences. 



Table 9G. 



Pressure at Fr<uiiheim, Fchniunj 1911 to Jamiari) lUl'J. 

 Reduced to 32°F., £ea-lcvcl and gravity at 45". (luclics. 



In the last line tlie values have been smoothed by — — i ^'^"^ these are the best 



values obtainable for the yearly variation from the single year's observations. But these values 

 share in the abnormalities shown by the 1911 curve for McMuido Sound in figure 54. which 

 are very large ; hence the above series cannot be taken as a very near approach to the 

 normal yearly variation for Framheim. 



It is well known tliat the difference in pressure between two stations not too far apart 

 is much more constant than the jjressure itself. It is therefore very likely that the smooth 

 curve of prsssure difference between Cape Evans and Framheim given in figure 57 is not 

 widely different from the normal curve of differences which would be obtained from a much 

 longer period of comparison. We may therefore apply the appropriate monthly difference to 

 all the monthly values available for McMurdo Sound and get the normal pressure at Fram- 

 heim from the four years' observations in McMurdo Sound. The following table contains 

 in the fir.st line the smoothed pressure difference Cape Evans — Framheim measured from curve 

 I of figure 57 and in the second line these differences have been applied to the normal pres- 

 sure of McMurdo Sound to obtain th<^ normal pressure at Framheim. 



