53 



H. MOHN. M.-N. Kl. 



day from the 20*'' October to the 6*^'' November to the correction — 1.8 mm. 

 found in October at Framheim, I have calculated the corrections for those days. 



On the return jorney no observations of the hypsometers were taken. 

 After the return to Framheim 12 comparisons were made between the 

 station barometer and aneroid No. 4, on January 26^^^ to 29*'^ 1912, and 

 gave a correction of + o 6 mm. at 742.5 mm. Mean error of one compari- 

 son + 0.8 mm. When the Expedition started on the 20*^ October, 1911, 

 the correction at 742 mm. was — 1:8 mm. The change from — 1.8 to 

 ■+- 0.6 mm. or + 2.4 mm. in 99 da3'^s averages a change of + 0.024 mm. 

 per day. By adding 0.024 ^^- multiplied by the number of days that 

 had elapsed from the 18''' December, 191 1, when the Pole was left, to 

 the corrections found for the upward journey, I have tried to find the most 

 probable corrections for the aneroid readings on the return journey. 



From the 24^^^ midnight to the 28*^'' December 6 p. m. the reading of 

 the aneroid was constantly 19.20 inches or 487.7 mm. This striking absence 

 of oscillation in the barometer did not escape the attention of Capt. Amundsen, 

 but he was not able to give any reasonable commentary on it. I have 

 taken the extrapolated correction of + 3.0 mm. as the most probable. 



3. Wind. 



The observed Direction is true. 



The Velocity was judged and noted in metres per second. From the 

 daily observations with the hand-anemometer at Framheim, the observers 

 had acquired a consummate skill in judging the velocity of the wind. 



4. Cloudiness. Form of Clouds, Precipitation and Halos 

 were observed in the same manner as at Framheim. 



III. The Height of the Stations. 



The most rational method for computing the height of a station from 

 barometrical observations is to find the pressure at the lower level in the 

 vertical of the station and then calculate the difference of height from the 

 pressure and the temperature at the lower and the higher points. 



As P>amheim was the only station with continual observations, the 

 corresponding pressure of the base point could not be found by means 

 of a number of observations of pressure from stations surrounding the 

 upper station in question or by isobars drawn from such observations at 

 a known level. 



Meanwhile I have tried to construct such isobars in an indirect 

 manner. At the various stations Capt. Amundsen observed the direction 



