VOL. LXXVII.] PHILOSOPPHCAL TKANSACTIONS. 213 



by the green water, when exposed with fresh leaves, and when exposed with raw 

 silk ; and also to ascertain, at the same time, how long leaves, exposed in 

 green water, retain their power of separating from it, I made, 



Exper. 32. Two equal globes, a and b, containing 46 cubic inches, the 

 former a, filled with green potatoe water, strained through linen, and 4 peach 

 leaves ; the latter b filled with the same potatoe water, strained in like manner, 

 and J 7 grains of raw silk, were exposed from Sunday noon, Sept. 10th, till 

 Monday evening, the weather being cold, with many flying clouds, in all about 

 6 or 7 hours sun. The airs produced were as follow. 



Quantity. Quality. 



By the globe a, with green water and 4 peach leaves 2^ cubic inches 292 deg. 

 By the globe b, with green water and 1 7 grs. of raw silk 2^ 307 



Another globe c, filled with green water alone, was exposed at the same 

 time , but it was broken by an accident before the experiment was completed. 

 The two globes, a and b, with their contents, being again exposed from Tues- 

 day noon till Thursday evening, yielded air as follows. 



Quantity. Quality. 



The globe a, with the peach leaves ^-r^jy cubic inches 344 degrees. 

 The globe b, with raw silk ^^ 350 



The weather on Tuesday and Wednesday was cold, with very little sunshine \ 

 but Thursday was a very fine warm day, when the greatest part of the air was 

 produced. This air was removed and proved on Friday morning Sept. 15. 



Perhaps all the appearances above described might be satisfactorily accounted 

 for, by supposing the air produced in the different experiments to have been 

 generated in the mass of water by the green matter; and that the leaves, the 

 silk, &c. did no more than assist it in making its escape, by affording it a con- 

 venient surface to which it could attach itself, in order to its collecting itself 

 together, and taking on itself its elastic form. The phenomena might also be 

 accounted for by supposing the green matter to be a vegetable substance, agree- 

 able to the hypothesis of Dr. Priestley, and that attaching itself to the surfaces 

 of the bodies exposed in the water, as a plant is attached to its soil, it grows ; 

 and, in consequence of the exertion of its vegetative powers, the air yielded in 

 the experiment is produced. 



I should most readily have adopted this opinion, had not a most careful and 

 attentive examination of the green water, under a most excellent microscope, at 

 the time when it appeared to be most disposed to yield pure air in abundance, 

 convinced me, that, at that period, it contains nothing that can possibly be sup- 

 posed to be of a vegetable nature. The colouring matter of the water is evi- 

 dently of an animal nature, being nothing more than the assemblage of an 

 infinite number of very small, active, oval-formed animalcules, without any 



