INTRODUCTION. 



time, and the totals for each hour in hours and decimal parts of an hour are recorded 

 in the tables. The column to the right, headed Amount, contains the total recorded 

 for each day, the greatest daily amount being printed in bold-faced type. The other 

 column to the right, headed Total Possible, contains the hours and fractions of an 

 hour between sunrise and sunset on a level horizon for each day. At the foot is 

 given the sum total of each hour for the month. 



Wind. — The direction and force of the wind are noted at each hour, the observer 

 while doing so standing on the flat roof of the Observatory. During summer a 

 Robinson Hemispherical Cup Anemometer is mounted on the top of the Observatory 

 Tower; it is connected by a shaft to a counter inside the top room of the tower, 

 where the number of revolutions is read off hourly. From the velocities so obtained 

 the average equivalent in miles per hour of the scale of wind-force used in the direct 

 observation of the wind has been computed : it is as follows — 



Wind Force 







1 



2 



3 



4 



5 



6 



7 



8 9 



10 



11 



12 



Miles per hour 







6 



12 



21 



30 



39 



49 



60 



72 (84) 



(97) 



(112) 



(130) 



The values for Force 9 and upwards must be regarded as rough approximations 

 only. 



In the printed tables the direction of the wind to 16 points and the force on 

 the above scale are entered. Each month occupies a page, the upper part contain- 

 ing the entries for 1 to 12 hours, with on the right a column headed Max. giving 

 the highest wind-force observed in each day ; the lower part gives the afternoon 

 values and the daily means of the wind-force. At the foot of each part are given 

 the hourly mean values of the force, and at the bottom of the page the total 

 number of observations of each direction of wind during the month. Near the end 

 of the volume (p. 420) will be found tables of the mileage recorded by the anemometer 

 during such times as it was working. 



Cloud. — The Species and Amount, on the scale to 10, of cloud at Ben Nevis 

 Observatory are noted at each hour by the observer. In the tables as printed the 

 amount only is given ; indicates that the sky is clear from 30° above the horizon 

 upwards, and 10 that it is overcast. When the summit is covered with fog or 

 mist so that the sky cannot be seen the symbol = is used, and this is reckoned as 10 

 in computing the averages for the day and month. The right hand column in each 

 month contains the mean for the day, and at the foot the mean value for each hour 



is given. 



Fort- William Observatory. 



The. Observatory in Fort- William, which was equipped by the Meteorological Council 

 as one of the Council's Observatories, was opened in 1890, and from 1st August of that 



