from Water exposed to Light. 203 



them in the manner above described, I proceeded in the 

 course of my experiments as follows. 



Finding that raw silk, exposed in water to the action 

 of light, causes the water to yield pure air in so great 

 abundance, I was desirous of finding out whether this 

 arose from any peculiar quality possessed by the silk ; or 

 whether other bodies might not be made to produce the 

 same effect : to this end, having provided 6 globes, each 

 about a^\ inches in diameter, and having filled them with 

 fresh spring-water, I introduced into them the following 

 substances, and exposed them all at the same time to the 

 action of the sun's rays. 



In the globe No. i. I put 15 grains of sheep's wool, 



No. 2. 15 grains of eider-down, 



No. 3. 15 grains of the fine fur of a 



Russian hare, 



No. 4. 15 grains of cotton-wool. 



No. 5. 15 grains of lint or theravel- 



ings of fine linen, 



No. 6. 15 grains of human hair; 



these substances being all well washed, and being thor- 

 oughly freed of air by being wetted before they were put 

 into the globes. 



The results of these experiments were as follows. 



Experiment No. 6. 



The globe No. i, which' contained the sheep's wool, 

 did not begin to furnish air in any considerable quantity 

 till the third day of its being exposed to the action of the 

 sun's rays ; and, several days of cloudy weather interven- 

 ing, I did not remove the air till the eighth day, when I 

 collected if cubic inch, which, proved with nitrous air, 

 gave I a-\- i^n=^ 1.28, or 272 degrees. 



