54 



Mr. J. B. N. Hennessey. 



[May 25,. 



listed throughout the year's work at any one station, but as already 

 remarked, I think a pair of stations essential. No doubt several pairs 

 are really wanted, and sooner or later I believe this will come to be 

 established right round the globe, for actinometer and solar photography 

 and physics generally : at any rate this must happen, so soon as the 

 leading nations of this earth take home to themselves the fact, that 

 solar energy is the great force which utterly governs them, indirectly 

 perhaps even in matters of commerce or war. Meanwhile, even one 

 pair of actinometer stations will be welcome, and all the more so if 

 established at once, 



