NO. 17.] WIND. COMPASS. ANEMOMETER. 



WIND. COMPASS. ANEMOMETER. 



The direction of the wind was always observed by the ship's steering- 

 compass. This stood on the after-deck in front of the wheel. The direction 

 was noted to the nearest point of the compass. 



The velocity of the wind was measured with Mohn's hand-anemometer.^ 

 A description of this instrument is to be found in the 'Norwegian North 

 Atlantic Expedition 1876—1878', Second Volume, Meteorology, pp. 6 to 10., 

 and in the Quarterly Journal of the Meteorological Society (London) for 

 January, 1878, pp. 37—39. The instrument used on the Fram was iden- 

 tical with that used on the North Atlantic Expedition in 1877 and 1878 and 

 also at the Norwegian Polar Station at Bossekop in the Polar Year 1882—83. 

 Its friction-coefficient was found, from experiments made before the departure 

 of the Expedition, to be I'O metre per second, and this value has been 

 adopted for the computation of the true velocity of the wind. 



In order to find the true direction and velocity of the wind from those 

 observed, we must make use of a special method of computation in the 

 case of the ship being in motion. The method used in this case I have 

 fully explained in the above-named memoirs (North At). Exp., pp. 10—30; 

 Qu. Journ. Met. Soc, pp. 39—41). When beating along the Siberian 

 coast against a head-wind, the Fram made much lee-way. The angle 



' A smaller English registering anemometer was placed on a stake on the ice, and read 

 every day; but it often broke down, and was subsequently turned into an odometer. 



