60 REPORT~1886. 



at 9 A.M. of the 11th, about which it remained till 4 r.M. of the 12th, 

 when it fell either to a calm or the lightest airs from the north-east, when 

 the greatest dryness took place. On these two days the extremes of tem- 

 perature were 24-3° and 13-3° ; and at 8 a.m. of the 12th, while the tempe- 

 rature at the observatory was 23-9°, in Fort William it was 19*2°, or 4-7° 

 lower than on the top of Ben Nevis. 



During the twelve months the Sunshine Recorder registered 111 hours 

 of sunshine, which is about 19 per cent, of the possible sunshine. In the 

 previous year the hours of sunshine only amounted to 464. The extreme 

 months were July, with 162 hours, and January, with only 15 hours of 

 sunshine. The observations of the two years show that the annual period 

 of daily maximuin sunshine is the four hours from 9 A.M. to 1 P.M., the 

 means being 61, 67, 67, and 65 hours respectively. For the six months 

 from April to September the hour of most sunshine is from 8 to 9 a.m., 

 the mean being 39 hours. From this time it slowly but steadily diminishes 

 to 36 hours for the hour ending 1 p.m., and from 4 to 5 p.m. the number 

 has fallen to 26 hours. The numbers for the five hours preceding, and the 

 five hours succeeding noon, are respectively 38 and 32 hours. The total 

 number of hours for the six months, from January to June, is 294, and 

 for the second half of the year 326 hours, the difference being wholly due 

 to the exceptionally large amount of sunshine in July and August 1885. 

 In truth the distribution of the sunshine through the year cannot be said 

 to be dependent on the great annual rise and fall of temperature, but on 

 those causes which bring anticyclones over Ben Nevis. 



The rainfall for the year ending May 1886 amounted to 128"34 

 inches, the largest monthly fall being 24-33 inches in December 1885 and 

 the smallest 2-85 inches in February following. The heaviest precipita- 

 tion on any day was 534 inches on December 12, and 445 inches on 

 January 1 — these being heavier than any previously recorded daily falls. 

 On the two days December 12 and 13 the precipitation amounted to 

 8-86 inches. For five-day periods the following heavy falls are recorded : — . 

 for the five days ending December 15, 10-25 inches ; October 5, 10-02 

 inches ; January 3, 9-25 inches ; and September 16, 6-13 inches. 



On the other hand, the year was marked by the large number of days 

 on which either no rain fell or on which the amount was less than O'Ol 

 inch. The number of these days amounted to 126, being thus in the 

 proportion of two rainy days for each fair day. The largest number of 

 fair days in any month was twenty in August, and the least, two, in Sep- 

 tember. In the previous year there were only seventy-nine days without 

 rain, being thus forty-seven fewer than last year. 



In the meantime, the whole of the hourly observations of the observa- 

 tory, and the observations of the station at Fort William down to date 

 are in the press. The publication will appear as an extra volume of the 

 ' Transactions of the Royal Society of Edinburgh,' and by this handsome 

 act on the part of the Royal Society these observations will shortly be in 

 the hands of scientific men in all parts of the world. 



In connection with the Ben Nevis observations the investigation of 

 the important question of the bearing of the results on the weather of these 

 islands steadily advances. The position of the observatory on an elevated 

 isolated peak, and that of the low-level station at Fort William, being 

 close to the sea and on a bank sloping down to it, renders this pair of 

 stations second to none anywhere yet established for the investigation of 

 some of the fundamental data of meteorology. Among the more im- 



