METEOROLOGICAL OBSERVATIONS OF BEN NEVIS. 281 



26 in September, and at Fort William twenty-four in March, and the 

 minimum number sixteen in January and again in February at the top, 

 and fifteen in April at Fort William. 



During the year the number of days on which 1 inch of rain or more 

 fell was forty-nine at the top and fourteen at Fort William ; at the latter 

 place an inch of rain did not fall on any day in January, April, and June. 

 At the top this amount was exceeded on eight days of November, and 

 seven days both in September and December. 



Auroras are reported to have been observed on the following dates : — 

 February 26 ; March 3, 29, 30, 31 ; April 2, 5, 6, 23, 24, 25 ; October 1 ; 

 December 20, 21, 22, 23, 24 ; the number being thus relatively few, the 

 sun spots being near the minimum of the eleven-year period. 



St. Elmo's Fire was seen on March 10, 24 ; May 13 ; December 29, 30. 



Zodiacal Light, not observed during the year. 



Thunder and lightning was reported on April 15 ; August 5 ; 

 December 8, 29. Lightning only, July 24 ; August 1, 2, 4, 13. 



Solar Halo, March 30 ; April 27 ; May 27 ; August 1, 3 ; September 

 10, 11, 26; October 4, 20. 



Lunar Halo, January 13, 21 ; February 12 ; May 13 ; August 9, 12, 

 22 ; October 4 ; November 10, 16. 



As stated in our last Report, the observations at the intermediate 

 station on Ben Nevis, at a height of 2, 322 feet, were resumed in the summer 

 months. The observations were made from July 19 to September 30, by 

 Messrs. T. S. Muir of the Royal Hill School of Edinburgh, Alexander 

 Drysdale, B.Sc, Dollar, and A. Aitken. By the great enthusiasm and 

 self-denial of the observers, aided by several self-recording instruments 

 gifted by Mr. J. Y. Buchanan, an invaluable complete series of hourly 

 observations have been obtained. Hence, for the first time, complete 

 series of hourly observations have been secured at heights of 42 feet, 

 2,322 feet, and 4,407 feet, the three places being in the same line and 

 differing but little in horizontal distance from each other. These hourly 

 observations from the three Observatories on Ben Nevis are really 

 indispensable data in investigating the problems relating to the vertical 

 gradients of the temperature, pressure, and humidity of the atmosphere 

 and its movements. 



Messrs. Muir and Drysdale have undertaken, under the superinten- 

 dence of the Directors, the laborious work of discussing these observations, 

 and at the Meeting of the Scottish Meteorological Society, Mr. Muir sub- 

 mitted an elaborate preliminary report. Among the important results 

 either disclosed or indicated in the discussion may be noticed the relations 

 which obtain between different vertical distributions of temperature and 

 pressure on the one hand, and cyclones and anticyclones on the other, 

 thus : — When the reduced barometer at the Ben Nevis Observatory, for 

 a series of observations, comes out higher than that of Fort William, 

 the accompanying disturbance of temperature takes place in the lower half 

 of the mountain, that is, below the intermediate station, and denotes the 

 approach of an anticyclone. Conversely, when the reduced Ben Nevis 

 Observatory barometer reads lower than that of Fort William, then the 

 disturbance of temperature takes place in the upper half of the mountain, 

 and denotes the approach of a cyclone. 



In the further prosecution of this line of research, it has been 

 arranged that in the summer of 1898, in addition to the hourly observa- 

 tions, the observers make temperature and humidity observations at 



