METEOROLOGY OE BEN NEVIS. XXXV 



ently by the observers in all seasons, hours, and weathers. Generally the 

 observations are wanting for the same hours that the temperature observations 

 are wanting ; and as in the case of temperature, the omitted hours have been 

 interpolated, aided by occasional remarks in the sheets of daily observations ; 

 and since the omissions nearly all occurred in rough and stormy weather, the 

 interpolations are tolerably correct. 



An anemometer, specially designed by Professor Chrystal for the Observa- 

 tory, was erected in October 1884. Unfortunately, however, in the colder 

 months, the deposition of ice crystals renders all anemometers utterly useless 

 except on rare occasions, and during a brief season of the year. An important 

 service has, however, been rendered by this anemometer. A sufficient number 

 of observations of the wind's velocity have been obtained by it to enable Mr 

 Omond to assign numerical equivalents in miles to the estimations of the force 

 of the wind.* The equivalents to force are as follow : — 



Estimation Scale. 



Equivalent in 



miles per hour 



1 



5 miles. 



2 



12 



» 



3 



21 



» 



4 



30 



J3 



5 



39 



3) 



6 



50 



y> 



7 



61 



?» 



8 



73 



)> 



9 



85 



") 



10 

 11 



96 



108 



"I Higher 



12 



120 



J 



For the higher velocities the number of observations with the anemometer 

 was insufficient for a trustworthy comparison. 



The daily maximum velocity of the wind (Table IV.) occurs during the 

 night, and the minimum during the day. The daily differences are greatest in 

 summer and least in winter. In summer the maximum, 2 21, occurs at 4 a.m., 

 and the minimum, 1*68, at 2 p.m., or at the rate of 14 and 10 miles an hour 

 respectively. In winter the daily extremes are 3*45 at 4 a.m. and 315 at 2 p.m., 

 or 26 and 23 miles an hour. It will be observed that while on the mean of 

 the year the maximum may be considered as occurring during the four hours 

 from midnight to 4 a.m., the minimum is spread over eight hours from noon 

 to 7 p.m. Another peculiar feature of the daily curves is a slightly marked 

 secondary maximum from 3 to 5 p.m. during the five months from April to 

 August, a peculiarity which also appears in the annual curve. These results are 

 the reverse of what obtains in lower situations and over extensive plateaux, or 

 where the wind, before reaching the Observatory, has blown over some extent 



* See Proceedings, vol. xiii. p. 839. 



