INFLUENCE OF HIGH WINDS ON BAROMETER AT BEN NEVIS. 



493 





door, and windows, these results may be regarded as applicable to the readings of 

 barometers generally, since they are in almost every case suspended in situations similar 

 to that of the Ben Nevis barometer. 



In a paper on the Mean Atmospheric Pressure of the British Islands, published in 

 the Journal of the Meteorological Society,* monthly and annual isobars are given for 

 every two-hundreths of an inch of pressure. These isobars show a lower pressure than 

 •elsewhere over those parts of the country where the prevailing winds are stronger. 

 It may be regarded as highly probable that in many cases the curved courses taken 

 by the isobars do not indicate any real lowering of atmospheric pressure over these 

 districts, but are only an increased depression of the barometer brought about by the 

 strong winds which prevail more frequently in those parts of the country. 



In working out the question of the barometric gradient from actual observations, 

 particularly the relations of the higher gradients to the wind velocities, the results 

 hitherto arrived at cannot be said to be quite satisfactory. The reason is that, while 

 the wind velocities were known with tolerable accuracy, the pressure of the free atmos- 

 phere could not be dealt with, because the observations did not record it ; what the 

 Observatories recorded was only the barometric readings. For such discussions to be 

 satisfactory, the amount of the depression of the barometer, owing to the force of the 

 wind prevailing at the time, should be approximated to and allowed for. 



PART II. 



In preparing the data for Part I. it was evident that the results differed, in many 

 .cases in a remarkable degree, with different winds according to their directions. 

 Accordingly the next step in the inquiry was to treat each wind direction separately 

 to sixteen points of the compass, N., N.N.E., N.E., etc. The mean amounts of the 

 barometric depression for each wind, according to its strength, are specified in the 

 following table. Calms include all winds whose velocity was less than 6 miles an hour. 



Force — 



Miles 



N. 



X. N. E. 



N.E. 



E.N.E. 



K. 



E.S.E. S.E. 



S.S.E. 



s. 



s.s.w 



s.w 



w.s.w. 



vv. 



W.N.W. 



N. W. 



N'.N.W. 



Beaufort 



per 

































Scale. 



hour. 



Inch. 



Inch. 



Inch. 



Inch. 



Inch. 



Inch. Inch. 



Inch. 



Inch. 



Inch. 



Inch. 



Inch. 



Inch. 



Inch. 



Inch. 



Inch. 



Calms. 







■009 



■on 



■014 



■013 



■013 



008 -005 



•002 



■001 



■003 



•004 



■006 



■006 



■004 



•003 



■005 



1 



6 



■009 



■012 



•012 



■014 



■007 



■001 "004 



•004 



•003 



•001 



•001 



■000 



■002 



■004 



■006 



■009 



2 



12 



■020 



■025 



•028 



■025 



■016 



■008 -003 



•000 



•000 



■001 



■002 



■000 



•000 



■001 



■007 



•014 

 ■021 



3 



21 



■028 



■035 



•037 



■031 



•022 



•012 -00S 



•004 



■003 



■004 



■007 



■006 



■006 



•008 



■014 



4 



30 



■034 



■044 



■047 



■043 



■03,3 



•023 -015 



■009 



•005 



■004 



•006 



■006 



■005 



■003 



•013 



■034 



5 



39 



•052 



■054 



•054 







■028 -024 



■018 



•012 



■010 



■010 



■012 









6 



49 



■066 











■036 '' -035 



•026 



■022 



■017 



■017 













7 



60 



■084 











•055 -053 



■O44 



■O44 

















8 



72 













■080 -072 



•060 



■054 

















9 



84 













■107 





















10 



97 













■126 





















11 



112 













•150 















... 







11 to 12 



13() 











... 



■170 















... \ 







* Journal Scot. Meteorol. Soc, vol. vi. p. 4. 



