INSTRUMENTS AND METHODS. 



165 



barometers at the two stations was desirable. Unfortunately no direct comparLson was then 

 possible, but that there was no appreciable instrumental error could be determined indirectly, 

 as follows. 



At the end of January 1911 the Terra Nova left McMurdo Sound to proceed to King 

 Edward VII Land, where it was intended to establish the eastern pai-ty. When she was in 

 McMurdo Sound her barometer was compared with the one in use at Cape Evans. As she 

 proceeded eastwards the ship's barometer fell continuall}' compared with tha readings at Cape 

 Evans, thus confirming the fall in pressure over the east of the Ross Sea. As is well Icnown 

 the Terra Nova encountered tbe Frain in the B-iy of Whales and during Febraary 4, 191], 

 the two ships were near to one another. From thiir meteorological logs the following com- 

 parison of the barometer readings is possible. 



Table 93. 

 Barometer Comparison. 



From this it will be seen that the two ships' barometers were in satisfactory agreement 

 while the Cape Evans' pressure was -30" higher than the simultaneous pressure in the Bay of 

 A\Tiales (Framheim). This result, so far as it goes, confirms the relative low pressure near 

 Framheim, but as the barometer on the Fram which is shown to agree with the one on the 

 Terra Nova was not the one which was subsequently used at Framheim, the desired comparison 

 of the Cape Evans and Framheim barometers was not effected. This final comparison, however, 

 is possible from the log of the Fram and the records of Framheim during the period in 

 January 1912 when the Fram was waiting in or near the Bay of Whales for the return of 

 Captain Amundsen's party from the South Pole. From January 14 to January 27, 1912 

 (inclusive), there were simultaneous observations on the Fram and at Framheim and these 

 with all corrections applied agree within -2 mm. of each other, the Framheim barometer 

 reading being the higher by this amount. 



Thus the Framheim barometer, through the intermediary of the barometers on the Terra 

 Nova and the Fram, was compared with the Cape Evans' barometer, and the comparison 

 shows that, if anything, the Framheim barometer read slightly higher than the Cape Evans' 

 barometer, which would tend to reduce and not increase the large pressure difference foimd 

 between the two stations. 



Method of Reduction of the Observations. — At Cape Evans twp Richard barographs were in 

 use from January 27, 1911, to the end of December, 1912. 



On January 24, 1911, the barometer was set up, but owing to the large amount of 

 work entailed in setting up the magnetic and meteorological instruments it was impossible 

 at first to take more than one set of meteorological observations each day. On March 2, 



