METEOEOLOGY OF BEN NEVIS. 



XXI 



tion purposes. The station selected at Fort- William is within a few yards of 

 the sea, and 29 feet above mean sea-level ; while the Observatory at the top of 

 Ben Nevis is built on a true peak. Both stations are therefore in positions at 

 which the effects of solar and terrestrial radiation are minimised. The observa- 

 tions of temperature at both stations thus closely approximate to the true 

 temperature of the free atmosphere — a condition of the first importance in 

 dealing with the larger questions in meteorology, which it is the chief object of 

 High-Level Observatories to elucidate. In these respects, no other pair of 

 Meteorological Stations anywhere in the world are so favourably situated as 

 these two stations for supplying the observational data required in investigating 

 the vertical changes of the atmosphere. The observations made at the Ben Nevis 

 Observatory and those at Fort-William are printed in extenso with this Report. 



Temperature. 



In the following table the mean temperature in each case is obtained from 



the formula — 



Max. + min. + 9 a.m. + 9 p.m. 

 4 



The means for both stations are for the four years since the Observatory 

 was opened, beginning with December 1883, and ending with December 1887. 





Jan. Feh. 



Mar. 



April. 



May. June. 



July. 



Aug. 



Sept. 



Oct. 



Nov. 



Dec. 



Year. 





Ben Nevis Observatory. 





1883, .... 

 1884 



25-6 



23-0 



24-6 



27-4 



33-1 



37-1 



41-6 



42-3 



40-0 



32-9 



26-2 



25-8 

 24-6 



31-6 



1885, .... 



24-2 



23-4 



22-3 



26-9 



26-8 



35-6 



42-3 



39-9 



34-8 



26-4 



28-5 



26 '2 



29-8 



1886, .... 



19-8 



21-1 



22-0 



26-8 



30-5 



36 



38-5 



39-9 



36-4 



34-6 



29-5 



20-2 



29-6 



1887, .... 



24-9 



27-1 



24-0 



25-6 



32-0 



45-5 



41-3 



40-0 



36-6 



28-4 



26-1 



22-8 



31 '2 





Fort- William. 





1883, .... 



1884, .... 



42-0 



41-4 



427 



45-5 



49-9 



54 '8 



58-2 



58-2 



54-9 



47 '9 



41-4 



41-0 

 39-4 



48-0 



1885 



37-4 



39 



39-8 



45-3 



46-0 



53 6 



56-4 



557 



51-2 



42-3 



41-8 



40-2 



45-7 



1886 



35-5 



34-8 



38-7 



44-0 



48-2 



53-3 



55-6 



55-3 



51-3 



49-4 



43-7 



34-3 



45-4 



1887, .... 



39-3 



40-5 



38-8 



42-8 



49-3 



58-3 



57-6 



56-4 



51-0 



44-8 



40-2 



36 '0 



46-3 



MeanB. N. 0.,. 



23-6 



23-6 



23-2 



26 7 



30-6 



38 '5 



40 '9 



40-5 



36-9 



30-6 



27-6 



23-9 



30-5 



„ F.-W., . . . 

 Difference, 



38 6 



38-9 



40-0 



44-4 



48-4 



55-0 



57-0 



56-4 



521 



46-1 



41-8 



38-2 



46-4 



15-0 



15-3 



16-8 



17-7 



17-8 



16-5 



16-1 



159 



15-2 



15-5 



14-2 



14-3 



159 



Rate of fall of temperature ) 

 with height, . . . \ 



292 



286 



261 



248 



246 



265 



272 



275 



288 



282 



308 



306 



275 



Thus the mean annual temperature of Ben Nevis for these four years is 

 30 o- 5, the lowest monthly mean being 23°2 in March, and the highest 40°*9 

 in July; August being nearly equal, viz., 40°*5. The difference between the 



