VOL. LXXVII.] PHILOSOPHICAL TKANSACTIONS. 205 



the place it occupied in the globe supplied with fresh water, I was desirous of 

 seeing what variation it would occasion in the result of the experiment, if, 

 instead of removing the air from time to time, I suffered it to remain in the 

 globe till the end of the experiment : to this end I made 



Exper. 14. In which the globe being filled with fresh water, and the silk used 

 in the last experiment, being first well washed, the whole was exposed 4 days to 

 the action of the sun's rays, the weathen being remarkably fine, and very hot. 

 On removing the air produced, I found it amounted to 30^ cubic inches ; and 

 its quality, proved with nitrous air, was la + 3 w = 1.02, or 298. 



Exp. 15. The silk employed in the last experiment having been frequently 

 used in the foregoing ones, I was desirous of seeing the effect of making use 

 of fresh silk ; and also of varying the proportion between the quantity of silk, 

 the quantity of water, and the size of the globe ; accordingly at 6 o'clock, p, m. 

 June 13, I filled a small globe, about 3 inches in diameter, which contained just 

 20 cubic inches, with fresh spring water, and 1 7 grains of raw silk, wound 

 in a single thread, which had never been put into water, or otherwise used, 

 since it came out of the hands of the si Ik- winder. At the end of 4 days, this 

 globe had only furnished -f of a cubic inch of air, which, proved with nitrous 

 air, gave la + In = 1.32, or 68 ; consequently was much worse than common 

 air. On the 18th, it began to produce good air, and during 6 hours of sun- 

 shine it furnished J-rVV cubic inches, which, proved with nitrous air, gave 

 la -j- 3n = 1.15, or 285. The two following days (viz. the 19th and 20th of 

 June) it furnished. l-^Vo- cubic inch of air, which, proved with nitrous air, gave 

 la + 3«=» 1.37, or 203; after which it totally ceased to yield air, though 

 exposed for several days in the sun's rays. Total quantity of air produced 2 , y^ 

 cubic inches ; mean quality la -|- 3w = 1.46, or 254. 



By this experiment it appears, that raw silk, when used for the first time, does 

 not immediately dispose the water to yield pure air ; on the contrary, that it 

 phlogisticates the air yielded by water to a very considerable degree ; and this I 

 afterwards found to be the case with several other substances. 



Though the quality at a medium, of the air furnished in this experiment was 

 not quite so good as that furnished in the two experiments last-mentioned (viz. 

 N° 13 and N° 14), yet its quantity, in proportion to the quantity of water made 

 use of, was greater than in either of them : it amounted to something more 

 than -i- of the volume of the water. 



Exper. 16. The great globe, contents 296 cubic inches, being filled with 

 fresh spring water, and 120 grains of poplar cotton, on the evening of June 9, 

 and being the next day exposed to the sun about 4 hours, on the morning of the 

 nth the air produced was removed, and its quantity was found to be If- cubic 

 inch. Its quality was very bad, viz. la -f- Iw = .l65, or 35 degrees only better 



