688 MR R. T. OMOND ON 



William during the night. That also occurs two or three days beforehand, and, 

 when strongest after sunset and before sunrise, points to a prolonged breakdown in 

 the weather.'' 



Mr Muir has thus shown that the combined temperature observations at the three 

 stations on Ben Nevis had a distinct predictive value, in addition to the information 

 they gave as to the vertical distribution of temperature up to 4400 feet altitude. 

 The readings taken in 1899 by Mr D. W. Wilton were in continuation of Mr Muir's 

 work, and confirm his conclusions. The main object of this paper is to put on record 

 and draw attention to the further set of observations taken in 1902 by Messrs J. H. M. 

 AVedderbtjrn and R. Aitken. 



The observations in 1902 were taken for only about three weeks, but were very full 

 and complete. They extended from the 6th to the 29th of August. From the 7th to 

 the 21st Mr Wedderburn and Mr Aitken, in addition to ten readings daily at the Mid- 

 Station, took temperature observations at certain hours at three additional stations, one 

 lower and two higher than the Mid-Station. These stations were all on the slope of the 

 hill-side, but, like the Mid-Station, were at places where there was a ridge or projection 

 that to a certain extent kept them apart from the main ascending and descending 

 currents of air on the hill-side. The heights of these three stations were respectively A 

 1800, B 2605, and C 3375 feet above sea-level, the Mid- Station being 2190 feet. 

 Temperature readings were taken at A at ll h and 16 h , at B at 12 h and 17 h , and at C at 

 13 h . On the 7th and 8th these observations were made with a sling thermometer, but all 

 the subsequent ones were taken with an Assmann psychrometer giving both dry and 

 wet bulb values. During this period, 7th to 21st August, observations of pressure, 

 temperature, cloud, and notes of weather were made at the Mid- Station at 9 h , 10 h , 12 h , 

 13 h , 14 h , 16 h , 17 h , 2 l h , and 22\ The readings at 9 h , 10 h , 14 h , 21 h , and 22 h were continued 

 till 29th August, when the station was closed. The rainfall at the Mid-Station was 

 measured twice daily, at 9 h and at 21 h . The barograph, thermograph, and hygro- 

 graph served as a check on the eye readings, and were used to interpolate any omitted 

 entries. 



The tables on page 691 contain the Mid-Station observations ; mean values are given 

 only for those hours at which the record extends from the 7th to the 29th inclusive, the 

 readings made on the evening of the 6th being not included in computing these means. 

 Interpolated values are indicated by brackets. 



Table I. — The barometer reduced to 32°, the first figure, always a 2, being omitted. 

 Any discussion of these readings would involve their reduction to sea-level, and com- 

 parison with the actual sea-level pressure as shown by the barometer at Fort- William. 

 This has not yet been carried out. 



Table II. — The amount of cloud, including fog and mist, which are reckoned as equal 

 to 10, observed at the Mid-Station. 



Table III. — Rainfall. The gauge was read at 9 h and 21 h , the totals for the 23 days 

 being 2 - 68 inches at 9 h and 1*57 inch at 21 h . Or, roughly, in the ratio of 10 to 6, 



