694 



MR R. T. OMOND ON THE MEAN DAILY TEMPERATURES AT THE 



temperatures. When the Schoolhouse temperature is above that at the Observatory 

 the difference is printed in heavy type, and when lower in italic type. 



Observatory . 

 School . 



1890. 



1891. 



1891. 



Aug. 



Sept. 



Oct. 



Nov. 



Dec. 



Jan. 



Feb. 



Mar. 



Apr. 



May. 



June. 



July. 



Aug. 



Sept. 



Oct. 



Nov. 



Dec. 



Year. 



55-3 

 55-9 



56-6 

 56-6 



49°-3 

 48-6 



42-8 

 42-0 



38°-l 

 37-2 



39°-l 

 38-5 



43°'2 

 43-0 



37°-4 

 37-6 



42°-6 

 42-6 



48°-2 



48-4 



57°-4 

 58 



567 

 57-3 



55°-5 

 56-2 



54°-l 

 54 7 



47°-0 

 47-1 



41-4 



40-8 



41-0 

 40-2 



47°- 

 47-0 



Difference . 



•6 -0 



•7 



■8 



■9 



■6 



■2 



•2 



■o 



■2 



■6 



■6 



•7 



•6 



•1 



•6 



•8 



■o 



These differences between the Observatory and the School temperatures show a 

 distinct though not very regular seasonal change. As the School temperatures are 

 employed for about one-third of the time discussed, viz. seven out of twenty years 

 from January to July, and six out of twenty from August to December, the following 

 corrections have been applied to the Fort-William table of mean values so as to make it 

 represent, as nearly as possible, what would have been the values had the Low-Level 

 Observatory been in operation during the whole period of twenty years : — 



Dates. 



Correction. 



Dates. 



Correction. 



January 



1-31 



+ 0°-2 



July 1-31 



-0°-2 



February 



1-28 



+ 0-1 



August 1-31 



-0-2 



March 



1-31 



00 



September 1 -20 



-o-i 



April 



1-30 



00 



September 2 1-Octr. 10 



00 



May 



1-31 



-01 



October 11-31 



+ 01 



June 



1-30 



-0-2 



November 1-30 



+ 02 





<■, 





December 1-31 



+ 0-2 



Table II. contains the temperatures at Fort- William, computed and corrected as 

 described. 



Difference of Temperature. — In Table III. is given the difference between the 

 values in Table I. and Table II. on each day of the year. 



The mean daily temperature at Ben Nevis ranges from 43° 7 on 28th June to 

 20° - 8 on 3rd March, a difference of 22° - 9. At Fort- William the warmest day is the 

 27th of June, temperature 58° - 6, and the coldest are the 12th and 13th of February, 

 each with a temperature of 37°' 1, thus giving a range of 21°'7. A period of twenty 

 years is, however, far too short to give satisfactory daily averages ; the disturbances of 

 temperature due to weather changes introduce fluctuations which are not eliminated in 

 twenty successive values. In Table IV. the values are smoothed, first, by grouping 

 them in fives and giving the temperature only for each five-day period, and, second, by 

 " Bloxaming " these values in successive threes. This process largely eliminates the 





