52 KEPOKT — 1888. 



Thus, Instead of the normal difference of 16°'0 between the top and 

 bottom of the monntain, it -was only 7°'0 during these four days, and, 

 instead of the air at the top being moister than at the bottom, it was 

 greatly drier. Hence the air at the top did not owe its great dryness 

 and high temperature to ascending enrrents from lower levels up the 

 sides of the mountain, heated by the strong insolation prevailing at the 

 time, but to descending currents from great heights, which are charac- 

 teristic of anticyclones, by which dryness and heat are developed much in 

 the same way as happens in the case of the Fohn of the lower Alps. So 

 markedly and so frequently did this type of weather prevail during June 

 that the mean temperature of the month at the observatory was only 

 12°-9 lower than that at Fort William, being the least monthly difference 

 hitherto observed during any season of the year. 



It may be here suggested that this peculiarity of anticyclones plays 

 a highly important and beneficial part climatically in mitigating the 

 rigours of winter_over those portions of Asia and America which are 

 almost continuously within extensive anticyclones during the winter 

 months. For the investigation of this phase of weather and cHmate it is 

 evident that the Ben Nevis observations afford data of the most invalu- 

 able description. 



To this report is appended Table I., giving the hourly deviations 

 from the mean atmospheric pressure for the months and the year, and 

 Table II. the deviation from the mean temperature calculated from the 

 four years' observations ending with 1887. 



It was hoped that the work of discussing the Ben Nevis observations 

 would by this time have extended farther than it has done beyond the 

 determination of the hourly constants of the more prominent meteoro- 

 logical elements in the direction of the investigation of the relations of 

 the observations to the weather of North-western Europe. But it was 

 found that the preparation of the observations for the press, and seeing 

 them through it, occupied much more time than had been anticipated. 

 Indeed, this work occupied the whole time of Messrs. Omond and Rankin 

 when they were in the office of the Scottish Meteorological Society, to- 

 gether with nearly the whole of the time of the treasurer's clerk ; and, 

 besides, since the beginning of the year less time has been at Mr. Buchan's 

 disposal for personally carrying out the laborious work of the discussion. 



In these circumstances the directors of the observatory have taken 

 into consideration the whole question, and are maturing a plan for a 

 thorough discussion of the Ben Nevis and Fort William observations 

 in their scientific and practical bearings, which they hope to complete in 

 the course of the autumn. This plan will require for the carrying of it 

 out a small additional staff working in conjunction with the office in 

 Edinburgh and the staff of the Ben Nevis Observatory for a period of at 

 least three years. 



In connection with the practical side of the inquiry your Committee 

 refer with the greatest satisfaction to the publication by General Greely, 

 chief signal officer of the United States Army, of Daily Weather Charts 

 of the Atlantic, beginning with October 1886. These charts have been 

 partially examined in connection with the Ben Nevis observations, and it 

 is not possible to overestimate their importance in the large inquiry now 

 in contemplation by the directors as to the relations of these observations 

 to the weather of North-western Europe, which is truly an international 

 undertaking. With the United States charts will be conjoined the obser- 



