514 



DK BUCHAN ON THE 



Next, on the days when the differences of the mean daily temperature were large, 

 exceeding 18°'0 or more, the mean pressure at Fort- William for the year was 0'320 inch 

 less than when differences of the temperatures were 12°*0 or less The differences for 

 the seasons were — winter, 0*268 inch; spring, 0*300 inch; summer, 0*298 inch; and 

 autumn, 0*403 inch. The greatest monthly excess was 0*446 inch in November, and the 

 least 0*153 inch in December. This remarkable difference in the results for these two 

 consecutive months arose from the varying intensity of the cyclones and anticyclones 

 in these months during the years under discussion. 



Class II. — The Mean Monthly Temperatures at both Observatories. 





Jan. 



Feb. 



Mar. 



Apr. 



May. 



June. 



48-3 



July. 



Aug. 



Sept. 



Oct. 



Nov. 



Dec. 



Year. 



Group I. — 



Temperature Differences, 

 all observed 



30-8 



31-5 



32-4 



37-2 



41-6 



497 



49'2 



45-8 



38-8 



36-0 



32-6 



39-5 



Group III. — 



Temperature Differences, 





























12° - or less 



28-6 



29-2 



36-8 



42-7 



47-4 



53-1 



54-0 



55-1 



50-4 



42-3 



35-5 



30-8 



42'2 



Group IV.— 



Temperature Differences, 

 18°'0 or greater . 



28-4 



28-1 



27-8 



33-7 



37-4 



43-0 



45-3 



45-5 



42-1 



35-8 



34-0 



33-7 



36-2 



Group III. — 



Compared with Group I. 



— 2-2 



—2-3 



+4*4 



+ 5*5 



+ 5-8 



+ 48 



+4-3 



+5-9 



+46 



+35 



—0-5 



—1-8 



+27 



Group III.— 





























Compared with Group IV. 



+02 



+11 



+90 



+100 



+10-0 



+101 



+87 



+96 



+83 



+65 



+1*5 



—2-9 



+6*5 



Thus, on comparing Group III. with Group L, it is seen that on the occasions when 

 the difference between the daily mean temperature was small, 12° *0 or less, the mean 

 temperature of the two Observatories exceeds the mean temperature of Group I., 

 when the difference between the daily mean temperature is the average. The excess 

 on the mean of the year is 2°*7. For the eight months from March to October, it is 

 continuously in excess ; the mean excess for these months is 5°*0. For the four months 

 from November to February there is, on the other hand, a deficiency amounting to a 

 mean of 1°*7. 



On comparing Group IV. with Group III. it is evident that when the difference between 

 the mean daily temperatures is 12°*0 or less, then the mean daily temperature of the 

 Observatories is 6°*5 higher than when the difference of the daily means is 18°*0 or 

 greater. The greatest excess extends over the seven months from March to September, 

 the mean then being 9°*2 ; and the least excess from November to February, when the 

 mean is about the average, falling, however, in December to a deficiency of 2° '9, the 

 exceptional character of the weather of this month having been equally noteworthy 

 as regards pressure and temperature. 



