MR. J. BAXENDELL ON SOLAR RADIATION. 147 



Mean Monthly Values. 



Max, in sun. Max. in shade. Diff. 



o o o 



January 47'44 4^76 4"68 



February 51*12 43"64 7'48 



March 56-30 45'84 10-46 



April 68-76 55'i4 lyBz 



May 74*56 59'8o 14*76 



June 78*26 64-30 13*96 



July 80-88 66-54 i4'34 



August 79-46 64*56 14-90 



September 75*24 61-82 13*42 



October 63*34 55'20 8-14 



November 53*46 47*58 5-88 



December 49*24 46-42 2-82 



IX. 071 Solar Radiation. Part. II. 

 By Joseph Baxendell^ F.R.A.S. 



Read before the Physical and Mathematical Section, Jan. 28th, 1868. 



It has been shown in the first part of this paper that the 

 curve laid down from the monthly means of solar radiation 

 derived from the five highest values in each month, or those 

 corresponding to the five clearest days, exhibits two max- 

 ima and two minima, occurring respectively in April and 

 September, and June and December. In order, however, 

 to determine the influence of the seasons upon the amount 

 of solar radiation on clear days, it will be necessary to 

 correct these means for the difference of meridian altitude 

 of the sun in the different months of the year. For this 

 purpose I have employed the Table given in the article on 

 Climate in the ' Encyclopaedia Britannica,^ referred to by 

 Sir John Herschel in a note at foot of page 1 1 of his ad- 

 mirable ' Treatise on Meteorology ;' and I have neglected, 

 as being immaterial for our present purpose, any correction 



l2 



