from Water exposed to Light. 199 



Experiment No. 4. 



Finding by the last experiment (No, 3) that heat 

 alone, without light, was not sufficient to enable silk in 

 water to produce air, I was desirous of seeing the effect 

 of light without heat upon them. To this end, I took 

 the globe B, with its contents, and, plunging it into a 

 mixture of ice and water, brought it to the temperature 

 of about 50° F. and taking it out of this mixture, and 

 exposing it immediately in the'sun's rays (which were very 

 piercing at the time), I entertained it in this temperature 

 above two hours by the occasional application of cloths, 

 wet in ice-water, to the lower part of the globe. 



Notwithstanding this degree of cold, a considerable 

 quantity of air was produced ; though it was not fur- 

 nished in so great abundance as when the globe was suf- 

 fered to become hot in the sun's rays. 



Having thus ascertained the great effect of the sun's 

 rays in the production of the air furnished upon expos- 

 ing silk in water to their influence, my next attempt was 

 to determine whether this arose from any peculiar quality 

 in the sun's light ; or whether other light would not pro- 

 duce the same effect. With a view to ascertain this point, 

 which I conceived to be of very great importance, I made 

 the following interesting experiment. 



Experiment No. 5. 



Having removed all the air from the globe B, and 

 having supplied its place with a quantity of fresh water, 

 so as to render it quite full, 1 replaced it, inverted, in its 

 jar, and, removing it into a dark room, surrounded it 

 with 6 lamps, with reflectors, and 6 wax-candles, placed 

 at different distances, from 3 to 6 inches from it, and so 

 disposed as to throw the greatest quantity of light pos- 



