from Water exposed to Light. 221 



air was collected, which, proved with nitrous air, gave 

 I a -\- 1 n 1. 1 2, or 88 ; after which, not a single air- 

 bubble more was produced, though the globe was exposed 

 a whole week in the window, during which, time there 

 were several very warm, fine, sunshiny days. 



This experiment shews evidently that something more 

 is wanting to the production of pure air by water, ex- 

 posed in the sun, than merely a surface to which the air 

 dissolved in the water can attach itself in order to its 

 making its escape. 



The air furnished in this experiment was doubtless 

 merely that with which the water, issuing from the earth, 

 was overcharged, and which would have made its escape 

 from the water, had the water, instead of being exposed 

 with the spun glass in the sun, been simply left for some 

 time exposed to the free air of the atmosphere. 



It appears that this air, naturally existing in spring- 

 water, instead of being dephlogisticated, is something 

 worse than common air ; and this agrees with the obser- 

 vations of Dr. Priestley, and seems to justify his opinion 

 with respect to the cause of the fertility of lands washed 

 by waters issuing from the earth. 



If the above experiment shews that something is want- 

 ing to be mixed with water in order to enable it to yield 

 pure air, when exposed to the action of the sun's light, 

 the following shew that this something, whatever it may 

 be, is frequently to be found in the water itself in its 

 natural state. 



Experiment No. ij. 



A large jar of clear white glass containing 455 cubic 

 inches, being washed very clean, was filled with fresh 

 spring-water, and inverted in a glass bason of the same, 



