102 



one may multiply the duration of sunshine by the percentage of 

 observed clearness and obtain the duration of sunshine for a special 

 station. But this will give us a value that is greater or less than the 

 value of the true intensity of sunshine according as the cloudiness 

 occurs mostly in the morning and evening or in the midday hours. 

 The only method for obtaining a satisfactory value of the intensity 

 of radiation as coming direct from the sun or as reflected from the 

 sky, the clouds, and the earth, is to maintain a self-registering acti- 

 nometer or, in place of that, frequent daily observations. 



In these tables I have adopted the division of each month into three 

 parts, as done by Libbey and occasionally used by meteorologists, but 

 the system of pentades, used by Dove, is often preferable; however, 

 this present system is convenient for monthly summations, and is also 

 used in the climatic table of Section II." 



Sums total of possible duration of sunshine, in hours, from January 1 up to any 

 day of the year. 



January 1-10 ... 

 January 11-20 .. 

 January 31-31 .. 

 February 1-10 . . 

 February 11-20. 

 February 21-28 . 



March 1-10 



March 11-20.... 

 March 21-31 .... 



April 1-10 



April 11-20 



April 21-30 



May 1-10 



May 11-20 



May21-31 



June 1-10 



June 11-20 



June 21-30 



July 1-10 



July 11-20 



July 21-31 



August 1-10 



August 11-20 ... 

 August 21-31 .... 

 September 1-10 

 September 11-20 

 September 21-30 



October 1-10 



October 11-20.... 

 October 21-31.... 

 November 1-10.. 



Num- 

 ber of ' 

 days. 



Hours. 

 104.0 



548.6 

 640.3 

 757.2 

 876.8 

 1,011.7 

 1,137.2 

 1,265.3 

 1,396.0 

 1,529.0 

 1,664.1 

 1,814.6 

 1,952.7 

 2,091.4 

 2,2,30.1 

 2,3as.2 

 2,505.2 

 2,654.1 

 2,787.3 

 2,918.1 

 3,059.2 

 3, 184. 7 

 3,307.4 

 3,427.4 

 3,544.6 

 3,659.1 

 3,782.1 



Hours. 

 97.7 

 197.2 

 309.5 

 414.9 

 523.7 



1,110.9 

 1,241.8 

 1,376.2 

 1,513.8 

 1,654.3 

 1,811.4 

 1,956.0 

 2,101.5 

 2,247.0 

 2,391.6 

 2,534.7 

 3,689.6 

 2,827.5 

 2,962.1 

 3,106.4 

 3,2:«.6 

 3,a57.1 

 .3,476.9 

 3,592.8 

 3,705.0 

 3,824.5 

 3,929.4 



a Omitted. 



