144 PROCEEDINGS COTTESWOLD CLUB 191 3 



inasmuch as there is more cloud in Winter than in Summer, 

 the whole effect of cloud is to accentuate rather than minimise 

 the difference caused by the seasonal change in the length 

 of the dayUght. 



Speaking roundly, possible sunshine is twice as great in 

 July as in January, but the actual number of hours of bright 

 sunshine 'experienced here is four times as great in July as in 

 January. 



In the foregoing table it will be noticed that the greatest 

 monthly average of bright sunshine for the 10 years stands to 

 the credit of July, whilst May, June and August have averaged 

 a nearly equal amount ; but the uncertainty in any particular 

 year occasioned by a cloudy wet period setting in during 

 either of the summer months to lessen the amount of bright 

 sunshine during that period is shown by the fact that the 

 amount of bright sunshine registered in Cheltenham was 

 greatest in one of the ten years in March ; in one year greatest 

 in April ; in three years greatest in May ; in two years greatest 

 in June ; in three years greatest in July. 



In May, 1909, when rain only fell in Cheltenham on 6 days 

 and the rainfall registered was but -89 inch, the bright sun- 

 shine for the month amounted to 284 hours. 



In August, 1912, when rain fell on 27 days, and 7 inches 

 were measured, there were only 90 hours of bright sunshine 

 in the month. 



From the Spring Equinox onwards, the amount of bright 

 sunshine increases with great rapidity. As over January and 

 February there is usually a large increase in April, the aver- 

 age bright sunshine of April being nearly three times that of 

 January. At the time of the Autumn Equinox, the lessening 

 of bright sunshine is just as rapid, with an average of above 

 four times more in September than in December, the last- 

 mentioned being the month of the whole year with least 

 bright sunshine and most cloud. 



Some of these points are useful to have in mind in regard 

 to the English climate generally and of that of Cheltenham in 

 particular when one is thinking of the effect of light and bright 



