METEOROLOGICAL OBSERVATIONS ON BEN NEVIS, 51 



a difference between the two temperatures distinctly less than the usual 

 difference, together with all cases where the temperature at the top ex- 

 ceeded that at Fort William at the time. It will be readily recognised 

 that this work is largely an inquiry into the anticyclone, and its connec- 

 tions with the cyclone and weather changes which accompany their 

 changing relations. 



Dr. Buchan's time has been largely occupied with the discussion of 

 the fogs observed at the Scottish lighthouses night and day from 1889 to 

 1899. These data, as stated, arc all entered on two daily maps, to each 

 of wliich are attached the weather maps of the Meteorological Office for the 

 day in question as issued in the weekly maps of the office, in addition to 

 which the daily direction and force of the wind at eleven selected light- 

 houses are given. Thus the general character of each day's weather is 

 readily seen, and the direction of the wind at the time the fogs were 

 recorded. The fogs here examined are not land fogs, but sea fogs, a 

 correct knowledge of which is of paramount importance to navigation. 



The more important results arrived at are these : — The annual maxi- 

 mum period is from April to June, and the minimum from October to 

 February, being thus generally the reverse of land fogs. The worst and 

 longest continued fogs occur with easterly winds, and their occurrence is 

 restricted to the east coast of Scotland. On the other hand, the fogs on 

 the west coast accompany westerly winds. These are much more frequent 

 and prolonged at places directly open to the Atlantic than at places such 

 as Rothesay, Oban, and Stornoway, which are sheltered from the Atlantic 

 by land of a greater or less extent and height. 



Conjoined with this discussion is the excessively heavy rain brought 

 by the easterly winds on the east coast of Scotland, and to a. greater or 

 less extent inland according to the height to which these rain-bringing 

 easterly winds extend in the atmosphere. On this point the conjoined 

 observations of the two Ben Nevis Observatories contribute invaluable 

 knowledge. 



An examination of daily weather maps of Europe constructed from 

 the daily weather maps of the British Islands, France, and Germany makes 

 it clear that these heavy rains and easterly winds occur when baro- 

 metric pressure dimiziishes from the Baltic and westwards through the 

 North Sea to the West of Scotland. It is here particularly to be noted 

 that at the same time humidities are high over those parts of the Con- 

 tinent whence these easterly winds have come prior to their arrival in 

 Scotland. Of these rain storms the great rains in the east of Scotland 

 on April 27 to 30, 1898, and on August 22, 1900, are among the most 

 remarkable ; they are therefore being investigated in great fulness of 

 detail. 



It will be known, from your Committee's previous reports, that gales 

 and storms of wind have for many years been observed night and day at 

 the Scottish lighthouses with a fulness and an accuracy attempted 

 nowhere else. Much time has been given to the discussion of these obser- 

 vations in their relations to the other weather phenomena charted on the 

 daily weather maps. One of the results already arrived at — and it is an 

 important one — is that the first step to be taken in any investigation of 

 storms is the partition of Scotland into eight or ten divisions based on 

 the physical features of the country in their relations to the more promi- 

 nent storm-bringing winds. The inquiry is therefore proceeding on 

 these lines. 



B2 



