NO. 17.] THE SLEDGE-EXPEDITION. 609 



THE SLEDGE-EXPEDITION. 



During Professor NANSEN'S and Lieut, (now Captain) JOHANSEN'S sledge- 

 expedition and wintering on Franz Joseph's Land in 189596, meteorological 

 observations were made almost every day, comprising wind, atmospheric pres- 

 sure, temperature of the air, amount and forms of cloud, and weather. 



The direction of the wind was noted by compass, and its velocity estimated 

 in metres per second. This estimation was based upon the practice which 

 the observers had gained on board the Fram when using the hand anemo- 

 meter mentioned on p. 3. 



For the observation of atmospheric pressure the expedition had two pocket 

 aneroids. The aneroid Hicks was divided into inches and the aneroid Gary 

 No. 4387 into millimetres. 



Before leaving the Fram, the aneroids were compared with the mercury- 

 barometers on board, Adie No. 763 and 764. The heights of the mercury- 

 barometers were reduced to 0, to the standard barometer and to standard 

 gravity. Seventeen comparisons made from the 22 nd to 25 th February, 1895, 

 gave the result, 



Correction for Hicks = 2'0 mm. 

 Gary = + 5'0 - 



In neither of the aneroids did the correction show any appreciable varia- 

 tion with pressure. 



The mean error of the correction found by one comparison was + 0'16 mm. 

 for each aneroid. The mean error of the pressure determined by the mercury 

 barometers is about O05 mm. This gives the mean error of a duly corrected 



reading of any of the aneroids equal to 



77 



