from Water exposed to Light. 207 



posed in 12 ounces of water 7 hours to the action of the 

 sun's rays, at a time when the weather was remarkably- 

 fine and very hot, furnished about f of a cubic inch of 

 air, which was so much worse than common air, that i 

 measure of it with i measure of nitrous air occupied 

 1.36 measures ; or it was i ^ -|- i ;z = 1.36, or 64. But 

 I lay no kind of stress upon the result of this experi- 

 ment, as it is more than probable that the badness of the 

 air arose from the roots of the plants ; for from the 

 leaves alone I have frequently since obtained air which 

 appeared to be considerably better than common air. 



From the leaves of the peach-tree I obtained an air, 

 which, proved with nitrous air, gave \ a -\- in ^:= i-32j 

 or 168 ; but I did not think it necessary to multiply 

 these experiments, particularly as Dr. Ingen-Housz and 

 Mr. Sennebier have given us the results of so many of 

 theirs upon the same subject, of the accuracy of which 

 there is no room left to doubt. I shall, therefore, con- 

 tent myself with referring to the results of their experi- 

 ments. 



With a view to determining, with greater precision, 

 the quantity and quality of the air produced by a given 

 quantity of water and of silk, exposed for a given time 

 to the action of the sun's rays, I made the following 

 experiment. 



Experiment No. 13. 



A globe of fine, clear, white glass, about Sj^q inches in 

 diameter, and containing 296 cubic inches, being filled 

 with fresh spring-water and 30 grains of raw silk, was 

 exposed in my window three days, viz. 12th, 13th, and 

 14th of May last (1786), these days being for the most 

 part cold and cloudy, with short intervals of sunshine. 



