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The Number of Gales Observed at the Ben Nevis Observatory. By Angus Rankin. 



The accompanying table shows, for the thirteen years, 1884 to 1896 inclusive, the 

 number of hourly observations at which the force of the wind was noted as above 6, on 

 the Ben Nevis scale of to 12. This is equivalent to all cases when the velocity of the 

 wind exceeded fifty miles per hour. The table gives the totals for each hour of the 

 day of the thirteen Januarys, thirteen Februarys, etc., in this period, with at the foot 

 the sum for each hour, which is the total number of cases observed at each hour during 

 the thirteen years. At the right hand of the table is a column giving the monthly 

 totals (the sum of the twenty-four hourly values) ; the gross total of the whole, amount- 

 ing to 3405 cases in the thirteen years, gives an average of 262 hours, or about eleven 

 days, per annum. 



But this total of 3405 cases is distributed in a very unequal manner throughout the 

 year — the month with the greatest number is January, 640 ; and the least, July, 48. 

 Gales are at Ben Nevis, as at other places in this country, essentially a winter phenom- 

 enon. In the seven months, October to April, there were in these thirteen years 

 2907 hourly observations of Gales, or a mean of 415 per month; but in the five 

 summer months, May to September, there were only 498 cases, a mean of 100 per 

 month, so that storms were more than four times as frequent in the former as in the 

 latter period. 



The 3405 cases of Gales are not distributed uniformly over the hours of the day, but 

 form a distinct diurnal curve, with two well marked maxima and two minima. If 

 equally divided, there would be 142 cases at each of the twenty-four hours of the day ; 

 but, as we see from the last line of the table, there are 166 at midnight, and 163 at 

 9h., these being the two maximum times, and only 138 at 5h., and 109 at 16h., these 

 beina: the minima, and the numbers at the intermediate hours lie between these values 

 in a fairly smooth and regular proportion ; thus the two maxima are of almost equal 

 value, but the afternoon minimum is far more pronounced than the morning one. 

 Most of the Gales tabulated blew from the southern half of the compass ; northerly 

 winds on Ben Nevis, though strong, are usually so squally and gusty that their average 

 pressure does not exceed force 6, and the fact that these Gales are mainly from one 

 direction (southerly) may give a clue to explain how in such stormy weather a distinct 

 diurnal period in their frequency is shown. It should also be noted that, when winds 

 of this strength are blowing on Ben Nevis, their direction is substantially the same as 

 the sea-level winds of the neighbourhood ; and as this direction is in general between 

 S.W. and E.S.E., the average isobars, both at sea-level and at the height of Ben Nevis, 

 will show a steep barometric gradient down to a centre of low pressure somewhere to 



