from Water exposed to Light. 197 



phial, made with the point of a diamond, the one shew- 

 ing i measure of my eudiometer, the other shewing 2 

 measures. 



The tube of my eudiometer is half an inch in diame- 

 ter internally, and i measure occupies 3 \ inches in length 

 upon it, and the measure itself is made of a piece of the 

 same tube. Both the one and the other are ground with 

 fine emery on the inside, in order to take off the polish 

 of the glass, and by that means facilitate the running 

 down of the water, which might otherwise hang in drops 

 upon the inside of the tube upon the introduction of air. 



The nitrous air was always fresh made, and of the 

 same materials, viz. fine copper wire dissolved in smok- 

 ing spirits of nitre, diluted with 5 times its volume of 

 water ; and all possible attention was paid to every other 

 circumstance that could contribute to the accuracy of the 

 experiments. 



I have thought it necessary to mention these particu- 

 lars, on account of the great difference in the apparent 

 goodness of any kind of air, proved by the test of ni- 

 trous air, which arises from the difference of the circum- 

 stances under which the experiments are made. 



But to return to my experiments upon the air pro- 

 duced upon exposing silk in water to the action of the 

 sun's rays. 



Experiment No. 2. 



Finding that the quantity and the quality of the air 

 produced depended in a great measure upon the inten- 

 sity of the light by which the water and the silk were 

 illuminated, I was desirous of seeing whether, by depriv- 

 ing them entirely of all light, they would not at the same 

 time be deprived of the power of furnishing air, To 



