Abstract of Paper on the Meteorology of Ben Nevis in Clear and in Foggy Weather* 



By J. Y. Buchanan, F.R.S. 



The publication by the Royal Society of Edinburgh of the hourly observations 

 made at the observatory on the summit of Ben Nevis along with corresponding 

 observations at Fort-William at the sea level is an important contribution to meteoro- 

 logical science. The study of this work reveals at once the important characteristic of 

 the Ben Nevis Observatory. It is situated on a true peak, and that the highest point 

 in the British Islands. Its height above the sea is such that it is usually enveloped in 

 cloud, and its records are for the most part those of an observatory established in the 

 clouds, and in an atmosphere habitually saturated with moisture. 



The weather on Ben Nevis falls naturally into three categories : the first includes 

 the days when the mountain is continuously enveloped in fog or cloud ; the second, 

 those periods when the mountain is clear of clouds ; and the third, periods during 

 which frequent alternations of clear and foggy weather occur. It is apparent that the 

 meteorological conditions of the locality will be best understood by studying the con- 

 tinuously clear weather and the continuously foggy weather, each by itself. It will then 

 be more easy to understand the conditions of mixed weather. When the meteorological 

 observations on Ben Nevis are looked at as physical observations, and the object is 

 to study the physics of the atmosphere, apart from all considerations of weather, then 

 a separation such as that above indicated becomes an obvious preliminary. Had 

 meteorology been first practised in the Tropics it would now be in a more advanced 

 state than it is. The meteorology of Europe, like the tides on its coasts, is the most 

 intricate and involved that can be found anywhere in the world, and it is the worst 

 possible material on which the study could be commenced. Within the Tropics, and 

 round the Poles, the conditions are simple and uninvolved, and the meteorological 

 observations, at least those made within the Tropics, reflect this simplicity. Generally, 

 in the Tropics there are two kinds of weather, indicated by the terms Dry season, 

 Rainy season. In Europe, we have dry seasons and rainy seasons ; but, whereas, in 

 the Tropics the dry season occupies completely one-half of the year and the rainy 

 season occupies completely the other half without any mutual interference, our wet 

 and dry seasons alternate as many times in the course of a single day. Here it would 

 seem to be indicated that we should do for ourselves what Nature does for us in the 

 Tropics, and sort out the weather before discussing it. 



The prime factor in determining the climate of a place is its Latitude, because this 

 determines the altitude to which the sun rises from day to day and the length of 



* Transactions of the Royal Society of Edinburgh (1S99), vol. xxxix. — Part III. No. 31. 

 BOY. SOC TEANS. EDIN. — VOL. XLIT. 3 O 



