METEOROLOGY OF BEN NEVIS IN CLEAR AND IN FOGGY WEATHEK. 



787 



tion should not be according to local apparent time, especially when, as at Ben Nevis, 

 hourly eye readings are made. They would be equally available for popular purposes, 

 whereas, the correction of popular time by as much as half-an-hour is a serious matter 

 for scientific purposes. When self-recording instruments are used, it is as easy to take 

 off the values for one time as for another. It is certain that it is apparent time and 

 not any conventional time that rules meteorological phenomena. 



Winds. — The data regarding the winds are contained in Tables lib to VIII. Tables 

 III. and VI. contain the total number of observations of each wind to sixteen points, 

 as logged in each month in clear and in foggy weather. Tables IV. and VII. contain 

 the same data reduced to eight points of the compass, and Tables V. and VIII. are these 

 figures reduced to percentages per month. 



Only the direction of the wind is given in the Tables. In foggy weather the 

 prevailing directions are N., N.W., W., and S.W., the greatest percentage being from 

 the West. In clear weather the prevailing directions are N., S.E., and S., with a 

 maximum at S.E., while calms occur very frequently. The cyclonic gales so common 

 on our coasts, especially in winter, blow hardest between S.W. and N.W., and on these 

 occasions the summit is usually enveloped in fog. On the other hand, in anti-cyclonic 

 weather the air has hardly any sensible horizontal motion, and is generally clear 

 and warm. 



In the following short Table are given the general results of the classification of the 

 winds according to percentage, and distributed over eight points of the compass : — 



Weather. 



N. 



N.E. 



E. 



S.E. 



S. 



S.W. 



W. 



N.W. 



Calm. 





Clear . . 



Foggy . . 



17-45 

 16-88 



601 



5-28 



11-63 

 3-63 



1885 

 5-64 



16-74 

 6-95 



8-94 

 17-82 



6-17 

 23-72 



3-54 



16-65 



10-67 

 3-43 



100 

 100 



If the winds were equally distributed round the compass we should have 12'5 per 

 cent, from each point. In clear weather the amounts are above the average for N., S.E. 

 and S. ; in foggy weather, they are above the average for N., S.W., W., and N.W. ; the 

 maximum falling on W., with 23*72 per cent., and the minimum on E., with 3 '63 per 

 cent. The winds in both clear and foggy weather require to be studied in connection 

 with the other meteorological elements, but for this purpose the individual observations 

 must be combined. It has not been possible to overtake this. 



Rainfall. — The data with respect to rainfall are contained in Tables IX. to XI. 

 Table IX. contains the total rain measured in each month of each year in continuous 

 clear weather. It will be seen that in weather of this description rain is of very rare 

 occurrence, so much so that the rain in clear weather is not further dealt with in 

 tabular form. Table X. is the corresponding Table for foggy weather. In this kind 

 of weather the rainfall is very large, and in Table XI. it is reduced to mean hourly 



VOL. XXXIX. PART III. (NO. 31). 6 G 



