NO. 17.] 



ATMOSPHERIC PRESSURE. 



395 



The 8-hours Period has very variable values for At, and small and 

 varying values for 3 from month to month. The value for a a for the year 

 comes out very insignificant. 



THE ANNUAL PERIOD. 



The mean pressure of the air for the different months is shown in the 

 following Table. This also gives the means for each month for 3 or 2 years 

 (August and September, 1893, excluded, as not being included in the drift of 

 the Fram), and the smoothed means (^U(a + 26 + c)) for each month. 



Mean Pressure of the air. 700 mm. 



The deviation fiom the mean rises in February and March to 12 mm. 

 and above, in December to upwards of 11 mm.; and the mean deviation 

 reaches to upwards of 7 or 8 mm. in December, February and March. The 

 monthly means computed are consequently very uncertain, and may be rather 

 far from the normal values. Unhappily there are no observations from stations 

 on the Siberian coast, by means of which we can reduce them to normal 



