1864.] Prof. Roscoe — Registration of Action of Daylight. 559 



The results of simultaneous measurements made at Heidelberg and 

 Manchester, and Dingwall and Manchester, are next detailed. 



From the integrals of daily intensity the mean monthly and annual 

 chemical intensity can be ascertained, and thus we may obtain a know- 

 ledge of the distribution of the chemically acting rays upon the earth's 

 surface, such as we possess for the heating rays. 



Figure showing curves of daily chemical intensity at Manchester, in 

 spring, summer, autumn, and winter. 



