THE 
LONDON, EDINBURGH anv DUBLIN 
PHILOSOPHICAL MAGAZINE 
AND 
JOURNAL OF SCIENCE. 
[FOURTH SERIES.} 
SEPTEMBER 1857. 
XVIII. On the Measurement of the Chemical Action of Light. 
By Joun W. Draver, M.D., Professor of Chemistry and 
Physiology in the University of New York*. 
pase recent experiments of Professor Bunsen and Dr. Roscoe 
encourage the hope that the attention of chemists will 
before long be particularly directed to photo-chemistry, which 
undoubtedly offers at this moment one of the most promising 
fields of research. 
To be satisfied what a boundless opportunity for investigation 
is here presented, it is enough to recollect that in the decompo- 
sition of carbonic acid by the solar rays lies the starting-point 
of all organization, both vegetable and animal; and that if it 
were not for that effect, the whole surface of our globe would be 
a mere desolate waste, presenting no appearance of life. Besides 
this relation to the world of organization, the influences of light 
are now recognized as occasioning combinations and decompo- 
sitions not inferior in number or importance to those produced 
by heat and electricity. 
Impressed by such considerations, I devoted a great deal of 
time some years ago to the study of the chemical action of light, 
as the readers of this Journal know. But at that period the 
attention of chemists was so completely absorbed in the depart- 
ment of organic analysis, and in the application of the discoveries 
so made to vegetable and animal physiology, that it seemed im- 
possible to divert it even to the fundamentul fact which in reality 
is at the bottom of all those investigations. Organization im- 
* Communicated by the Author. 
Phil. Mag. 8. 4. Vol. 14, No. 92. Sept, 1857. M 
