METEOROLOGY OF BEN NEVIS IN CLEAR AND IN FOGGY WEATHER. 



789 



Month. 



Clear Weather. 



Foggy "Weather. 



Number 

 of Hours. 



Total 



Rainfall 



in Month. 



Mean Rain- 

 fall per 24 

 Hours. 



Number 

 of Days. 



Total Rain- 

 fall in Month. 



Mean 

 Rainfall 

 per Day. 



Maximum 

 Rainfall in 

 one Day. 



Date of 



Maximum. 



January, 

 February, 

 March, . 

 April, . 

 May, . 

 June, 

 July, . 

 August, 

 September, . 

 October, 

 November, 

 December, 



606 



1,158 



1,335 



1,728 



2,228 



2,895 



1,502 



971 



1,296 



951 



983 



697 



luches. 



0-004 

 •033 

 •003 

 •110 

 •392 

 1-243 

 0-169 

 •720 

 •046 

 •064 

 •076 

 •000 



Inch. 



0-00015 

 •00069 

 •00005 

 •00153 

 •00422 

 •01030 

 •00270 

 •01777 

 •00085 

 •00161 

 •00185 



•ooooo 



86 

 54 

 78 

 59 

 27 

 42 

 46 

 58 

 79 

 64 

 88 

 66 



Inches. 

 93-029 

 68-587 

 82-602 

 34-782 

 20-555 

 32-579 

 41-452 

 55-852 

 101-646 

 74-438 

 91-660 

 71-049 



Inches. 

 1-082 

 1-270 

 1-059 

 0-590 

 0-761 

 0-776 

 0-901 

 0-963 

 1-2 6 

 1-163 

 1-042 

 1-076 



luches. 

 5-476 

 6-668 

 5-210 

 2-530 

 2-880 

 2-108 

 2-337 

 3-483 

 4-930 

 7-287 

 4-294 

 5-340 



Day. 



29 

 6 

 11 

 22 

 15 

 16 

 13 

 29 

 31 

 3 

 28 

 12 



Year. 



'92 

 '94 

 '90 

 '90 

 '92 

 '97 

 '90 

 '92 

 '91 

 '90 

 '93 

 '85 



Sums, . 

 Mean, . 



16,350 



2-860 



0-00389 



747 



768-231 



0-998 



4-379 







Barometric Pressure. — The particulars of barometric pressure are given in Tables 

 XIII. to XIX. Tables XIII. and XIV. contain the actual maximum and minimum 

 pressures observed at every hour during the thirteen years in clear and in foggy 

 weather. Tables XV. and XVI. contain the monthly mean hourly pressures for clear 

 and foggy weather. Tables XVII. and XVIII. contain the diurnal variations in the 

 monthly mean hourly pressures in clear and in foggy weather ; and Table XIX. gives 

 the monthly mean hourly excess of the barometric pressure in clear weather over that 

 in foggy weather. 



The last of these tables shows the most striking differ ence between clear and foggy 

 weather on Ben Nevis, namely, the large and continuous excess of pressure in clear 

 weather over that in foggy weather. At every hour of the year, without a single 

 exception, the mean monthly pressure is several tenths of an inch higher in clear than in 

 foggy weather. The maximum excess recorded in the table is 0'602 in. at twenty-one 

 hours in January, and the minimum is 0'296 in. at fourteen hours in February. 

 The average excess for the whole year is - 456 in., and the following are the mean 

 excesses for each month : — 



Jan. 



Feb. 



Mar. 



April. 



May. 



June. 



July. 



Aug. 



Sept. 



Oct. 



Nov. 



Dec. 



Mean. 



0-570 



0-320 



0-501 



0-353 



0-372 



0-390 



0-414 



0-433 



0-519 



0-550 



0-537 



0-513 



0*456 inch 



+ •114 



-•126 



+ •045 



-•103 



-•084 



-•066 



-•042 



-•023 



+ •063 



+ ■094 



+ •081 



+ •057 



o-ooo 



Eoughly speaking, in spring and summer the excess is below the mean, excepting 

 the month of March, and in autumn and winter it is above the mean. The drop from 



