Dr. Draper on the Decomposition of Carbonic Acid. 169 



proportional to the time that it takes to burn, because the con- 

 sumption in a given time depends upon that time. 



If, therefore, a thousand cubic feet of gas be charged 85. on 

 both sides of the river, it is clear that the consumers on the 

 south side pay at the rate of 95. 4c?. per cubic foot, because 

 they consume 7000 cubic feet in the same time that those on 

 the north side consume 6000. 



If Glasgow gas, Skaterigg gas and Lesmahagow gas are 

 each charged at 85. per 1000 cubic feet, the price paid by the 

 consumers will be 



s. d. 



1000 feet of Lesmahagow gas 8 



... Skaterigg gas 9 ^^\ 



... Glasgow gas 11 Q\ 



... south side river .13 Sf 



XXV. 'Note on the Decomposition of Carbonic Acid by the 

 leaves of Plants ujider the influence of Yellota Light. By 

 John William Draper, M.D., Professor of Chemistry 

 in the University of New York. 

 TN the year 1836 I discovered that the leaves of plants pos- 

 •^ sess the quality of effecting the decomposition of carbonic 

 acid under the influence of light which had passed through a 

 solution of bichromate of potash, and which was so completely 

 detithonized as to be unable to darken the chloride of silver. 

 Under the same circumstances also, young plants which had 

 been etiolated by germinating and growing in the dark, turned 

 green in a few hours by the fixation of carbon, so as to con- 

 stitute chlorophyll. Seeds also appeared to germinate with- 

 out any difficulty, and eventually produced vigorous green 

 plants. 



These results were published in 1837 in the Journal of the 

 Franklin Institute of Philadelphia*; I have likewise referred 

 to them in the Phil. Mag. (Feb. 1840). 



From time to time Mr. Hunt of Falmouth has called the 

 accuracy of these experiments in question, and having made 

 some investigations under the direction of the British Associ- 

 ation, at its expense, he has published reports on the matter. 

 It is the object of these publications to substantiate a doctrine 

 which is derived from Sennebier, that the blue and violet che- 

 mical rays are the true cause of the decomposition. 



That there might remain no reasonable doubt of the correct- 

 ness of the views I had given, I repeated the experiment of 



* I will take this opportunity to state that the experiments here alluded 

 to, with some others, are now collected together, and are in the press. They 

 will be in the hands of the English reader in a few weeks. 



