372 THE CHEMISTRY OF CREATION. 



every process it is probable that the whole three 

 forces are concerned -in all the phenomena of 

 growth, and in the various and complicated che- 

 mical process taking place in the plant. But, 

 at the three periods mentioned, it would seem 

 that each becomes, in succession, of the greatest 

 and most prominent importance to the plant. 

 In connexion with this most singular discovery, 

 is one equally singular and beautiful. It ap- 

 pears, from researches which have been carried 

 on with care for some years by Mr. R Hunt, 

 by means of an instrument called the actino- 

 graph, for measuring the intensity of the actinic 

 power at different periods of the year, that the 

 actinic rays are most active in spring, the light- 

 rays in summer, and the heat-rays in autumn. 

 Thus, by a beautiful adaptation, it is found that 

 the various periods of the life of plants requir- 

 ing the predominant influence of one or other 

 of these principles, are admirably connected 

 with those periods of the year when these prin- 

 ciples are most actively exerted. Thus, in 

 spring, the slumbering seeds require actinism to 

 awaken vitality in them ; and actinic power is 

 then most prominent in the sunbeam. In sum- 

 mer, they need to have their tissues condensed 

 and consolidated by the formation of wood, which 

 is performed by the aid of light ; and then the 

 light-rays are most powerful. In autumn, the 



