METEOROLOGICAL OBSERVATIONS OF BEN NEVIS. 



279 



weather of these two mont'as is well shown by the mean temperatures of 



the two Observatories, thus :- — 



Fort Ben Nevis 



"William. Observatory. 

 o o 



Change from September to October . —2-2 +12 



„ „ October to November . —3-2 —2-7 



,, „ September to November . —5-4 —1-5 



On the other hand, when the weather is strongly cyclonic, the reverse 

 liokls good. Thus in March the mean pressure was 0'300 inch under 

 the average of March, the weather being decidedly cyclonic, when the 

 change of temperature from February to March was + 1°"1 at Fort William, 

 but — 1°-8 at the top of the mountain. 



The following shows the deviations of the mean temperature of the 

 months from their respective averages : — 



Fort 



January . 



February 



March 



April 



May 



June 



July 



August . 



September 



October . 



November 



December 



Year 



Hence, owing to the frequent occurrence of well-marked and long-con- 

 tinued anticyclones, the mean annual temperature at the top of the 

 mountain was relatively one degree higher than that of Fort William ; 

 and the differences of the means of some of the months — notably of July 

 and October — were very striking. 



The absolutely highest temperature for the year recorded for Fort 

 William was 80°-4 on July 15, and at the top 64°-0 on July 16. The 

 absolutely lowest temperature was 20°'0at Fort William on December 23, 

 and at the top 4°-0 on January 25. The most noticeable feature of the 

 extreme temperatures at the top is the high extremes during October and 

 November when the anticyclonic type of weather was predominant. In 

 November, temperature rose on the 4th to 52°'0, being higher than 

 that recorded in any previous November. 



As regards the extremes of temperature, the difference between the 

 two maxima was greatest in April and May, when it was 22°'3, and least 

 in October and November, when it was respectively 9° "3 and 5° '8 ; and 

 the difference between the two minima greatest in January, when it was 

 20° '3, and least in December, when it was only 4° '9. 



The registration of the sunshine recorder at the top shows 813 hours 

 out of a possible 4,470 hours, being 118 hours more than in 1895, and 57 

 hours more than in 1896. This number of 813 hours is greater than any 

 annual amount recorded since 1891, but is 157 hours fewer than in 1888, 

 when the hours of sunshine numbered 970. The number 813 is 18 per 



