Dr. Gardner on the Action of Light upon Vegetables. 13 



The intimate relation which exists between the rays which 

 produce chlorophyl, the decomposition of carbonic acid, and the 

 luminous spectrum. The maximum for the formation of green 

 matter, has been shown to reside in the yellow ray. Dr. Draper 

 (Lond. and Edinb. Phil. Mag., Sept. 1843) discovered the maxi- 

 mum action, for the decomposition of carbonic acid, to be be- 

 tween the green and yellow, or more correctly, in the centre of 

 the yellow. Sir W. Herschel and Fraunhofer placed the maxi- 

 mum for light in the same space. 



(36.) The relation goes further ; for if the quantities obtained 

 by Dr. Draper for decomposing action, as measured by liberated 

 gas — Fraunhofer for illuminating power, determined by the eye 

 — and my estimate, obtained in time and by the eye — be ren- 

 dered commensurable and tabulated, they will give quantities 

 nearly allied. To produce such a table, I assume all the maxi- 

 ma equal to unity. My results being in time, and theirs in effect, 

 the inverse proportion is taken for each value given in Art. 14. 



Table showing the force of the solar rays, in producing the green color 

 of plants, the decomposition of carbonic acid, and illumination. 



Upon projecting these numbers, which although not rigorously 

 correct are very good approximations, the unity of the active 

 agent will be more strikingly exhibited. Let the axis of abscis- 

 sas be divided into intervals corresponding to Fraunhofer's col- 

 ored spaces, and the positions of the mean places of the dark 

 lines be marked from Mr. Powell's recent work on dispersion. 



