THE METEOROLOGY OF EDINBURGH. 



693 



Hence the frequency of rainfall is at a maximum on August 13, October 10, 

 and November 5, on each of which dates rain has fallen on fifty -five of the eighty-eight 

 years under review, while the smallest number of rainy days, viz., twenty -five, occurs on 

 March 8. 



Sunshine. 



Daily sunshine values have been calculated for thirty years. From 1861 to 1876 the 

 observations were made at Inveresk, 6 miles E. of the city. From 1877 to 1885 the 

 observer was Mr Blackwood, Cumin Place. No instrument was in use during the above 

 periods, the method adopted being to estimate the total sunshine recorded during each 

 day. From July 1890 to June 1895 the records are derived from a Campbell-Stokes 

 sunshine recorder in use at my station at Blacket Place. Owing to the shortness of 

 the period and the comparative looseness of the method of observing this element of 

 climate during the greater part of the period, the values given in Tables XX. to XXIII. 

 must only be regarded as tolerable approximations. 



Table XX. gives the mean number of hours the sun shone on each day of the year, 

 but in order to make the results strictly comparable the mean percentages which the 

 amounts recorded formed of the total possible sunshine for each day were computed. 

 The table given in the last edition of the Smithsonian Tables was the one from which 

 the total possible sunshine for Edinburgh was obtained. No allowance has been made 

 for the loss of sunshine which occurs near the time of sunrise and sunset owing to haze 

 at the horizon. 



The following are the variations in the mean percentage of possible sunshine from 

 month to month. (See Table XXI.) 





Greatest Percentage 





Least Percentage of 









of Possible. 



Date. 



Possible. 



Date. 



Range. 



January, . 



35 



25 



13 



4 



22 



February, 





35 



8 



20 



27 



15 



March, . 





42 



8 



23 



28 



19 



April, 





37 



30 



23 



5 



14 



May, 





38 



24 



24 



17 



14 



June, 





35 



21 



22 



3 



13 



July, 





38 



17, 20 



22 



26 



16 



August, . 





38 



23 



24 



8, 17 



14 



September, 





39 



11 



20 



22 



19 



October, . 





36 



2, 10 



19 



30 



17 



November, 





35 



10, 20 



17 



24, 27, 28 



18 



December, 





26 



23 



12 



18 



14 



Hence on the sunniest day of the year, viz., March 8, not half the possible 

 sunshine is recorded, while on December 18 we obtain only 12 per cent, of the total 

 possible. There is not much variation in the daily values from March to October, but 

 the dull period is well marked, extending from the middle of November to the end of 

 January. 



