H. MOHN. METEOROLOGY. [2nd. arc. exp. fram 



ATMOSPHERIC PRESSURE. 



The Barometer used in all the winter quarters was the Kew station 

 barometer Adie No. 850. It was compared with the standard barometer 

 of the Norwegian Meteorological Institute at Kristiania before starting 

 and after the return of the Expedition. The constant correction to the 

 true height of the barometer was found 



in 1898 to be — 0.042 millimetre ; M.E. = + 0.13 mm. 

 . 1903 - - —0.032 — »— „ „ +0.08 „ 



Mean —0.037 —y>— ±0.10 „ 



M. E. is the mean error of a single comparison. 

 The observations did not show any appreciable variation of the 

 error with pressure. The observations have been reduced with a con- 

 stant correction of — 0.04 mm. 



The barometer was suspended in the fore cabin with its cistern 

 2.8 metres above sea-level. 



The reduction to sea-level becomes + 0.285 mm. 

 Constant correction — 0.037 ,, 



Total correction +0.248 „ 

 From March 20 to April 20, 1900, the barometer was suspended 

 in the aft cabin, at a lower level, the corresponding reduction to sea- 

 level being 0.2 mm. less than that given above. 



The reduction to standard gravity has been computed by the for- 

 mula 



Gravity correction = 6 ( — 0.00264 cos 2(jp), 



6 being the height of the mercury, and cp the latitude. 

 For 1898 — 1899 I have taken the gravity correction 



and for the last 3 places 



+ 1.86 ^ mm. 



+ 1.79 ^ mm. 



