NO. 17.] BAROMETERS. 



There is consequently a most satisfactory accordance between the results 

 of the comparisons made on board and on shore. 



Adie 764 was observed in 1893, from July 21st to October 12th, from 

 Vardo until the Fram was frozen in, and in 1896 from August 14th to 

 August 19th, fi'om Spitzbergen to Norway. It was suspended in the chart- 

 house on the upper deck with its cistern 3"9 metres above sea-level. The 

 reduction of the barometric heights to sea-level has been taken as con- 

 stant and as + 0"38 mm. At 0° the entire reduction becomes 

 + 0-18 + 0-38 or + 0-56 mm. 



The mean error of a single observation of a Kew station barometer is 

 about + 005 mm. The mean error of a single observation of a marine 

 barometer at sea is hardly less than + 0"1 mm. The observers always noted 

 the nearest tenth of a millimetre. 



The Reduction to Standard Gravity. Scott-Hansen's pendulum-obser- 

 vations, and Professor 0. E. Schiotz's computations, have shown (Vol. II 

 No. 8) that the force of gravity observed during the expedition is in full 

 accordance with Helmert's formula 



gj, = 9-78 (1 + 000531 sin ^ cp) m. 



If the height of the barometric column as a measure of the true pressure 

 be B, the observed height (reduced to 0° and standard barometer) 6, the 

 standard gravity ^45, and the gravity at the place of observation gp , we have 



— =i^- B=b-^ 

 h gi5 ' gib 



Gravity-correction B-b = b(^ -l\ = h i^^^'A ■ 



From this formula was computed the following table for the values of 

 the gravity-correction as function of the latitude and the height of the baro- 

 meter. 



