Jhe Scientific Advantages of an Antarctic Expedition. 443 



Remarks by Br. Alexander Buchan. 



Dr. Alexander Buchan stated that his remarks would have exclusive 

 reference to the first two paragraphs of Dr. Murray's address, under 

 the heading of " The Atmosphere," but more immediately to the 

 relation between mean atmospheric pressure and prevailing winds. 

 He supposed he had been asked to speak on this occasion from the 

 extensive and minute knowledge of the subject he had necessarily 

 acquired in the preparation of the reports on atmospheric and 

 oceanic circulation which were published as two of the reports of the 

 scientific results of the voyage of H.M.S. " Challenger." 



The former of these reports on atmospheric circulation, is accom- 

 panied by twenty-six maps showing, by isobars for each month and 

 the year, the mean pressure of the atmosphere and by arrows the 

 prevailing winds of the globe, on hypsobathymetric maps, or maps 

 showing by shadings the height of the land and the depth of the sea ; 

 first, on Gall's projection, and second, on north circumpolar maps on 

 equal surface projection. The isobars are drawn from mean pres- 

 sures calculated for 1366 places, and the winds from even a larger 

 number of places distributed as well as possible over the globe. It 

 may also be noted that the figures showing the averages of pressure 

 and prevailing winds are published with the report, accompani- 

 ments to maps of mean atmospheric pressure and prevailing winds 

 of the globe not yet attempted by any other writer who has pub- 

 lished such maps. 



This, then, is the work undertaken and published in these reports, 

 which occupied seven years in preparing as time could be spared 

 from official duties. The result of the charting of the pressure and 

 prevailing winds is this : Stand with your back to the wind, then the 

 centre of lowest pressure that causes the wind is to the left in the 

 northern hemisphere and to the right hand in the southern hemi- 

 sphere, a relation well known as Buys Ballot's law. In charting the 

 1366 pressures and the relative prevailing winds no exception was 

 found in any of the two hemispheres. This is one of the broadest 

 generalisations science can point to, so far as regards what takes 

 place in the free atmosphere. 



Some years ago a theory of atmospheric circulation was published 

 by the late Professor Ferrel, which, as it is not accordant with the 

 broad results arrived at in the report on atmospheric circulation in 

 the " Challenger " reports, calls for serious consideration on account 

 of its bearing on any attempt proposed to be undertaken for the ex- 

 ploration of the Antarctic regions. 



One of the more recent expositors of this theory is Professor 

 Davis, of Harvard College, who, in his ' Elementary Meteorology/ 

 Boston, U.S.A., 1894, gives an admirable exposition of the results 



