48 ATMOSPHERIC ACTINOMETRY. 



actinic effect of twiliglit diirinu; e(|iial times of insolation <^oes on diniinisljing in 

 pioportictii as we ui)[)roacb the equator ami as the mean temperature rises. 



It would l>e interesting to ascertain whether tliis law continues into the 

 tropical regions. This is probable, but as yet is only a matter of conjecture. I have 

 taken the proper steps to begin observations on this subject early next spring. 



Whatever this extension may lead to. it is none the less unexpected to tiiid 

 that in our temperate regions, the most densely po])u]ated of the <,dol)e, the actinic 

 effect of the sun is, so to speak, in the opposite direction to its calorific influence. 

 The operation of this law on the flora cannot be doubted. Rut the futui'e alone 

 can tell us how this is brought al)out. 



