124- Sir Benjamin Thompson’s Experiments , &c. 
The phenomena might likewife be accounted for by fup~ 
pofing th e green matter to be a vegetable fubftance, agreeable to 
the hypothecs of Dr. Priestley, and that attaching itfelf to 
the furfaces of the bodies expofed in the water, as a plant is 
attached to its foil, it grows ; and, in confequence of the 
exertion of its vegetative powers, the air yielded in the experi- 
ment is produced. 
I fhould moft readily have adopted this opinion, had not a 
mod careful and attentive examination of the green water, 
under a mod: excellent microfcope, at the time when it ap- 
peared to be moft difpofed to yield pure air in abundance, con- 
vinced me, that, at that period , it contains nothing that can 
poffibly be fuppofed to be of a vegetable nature. The colour- 
ing matter of the water is evidently of an animal nature, 
being nothing more than the affemblage of an infinite number 
of very lmall, active, oval- formed animalcules, without any 
thing refetnbling tremella , or that kind of green matter , or 
water mofs, which forms upon the bottom and fides of the 
veflel when this water is fuffered to remain in it for a conli- 
derable time, and into which Dr. Ingen-housz fuppofes the 
animalcules above-mentioned to be actually transformed. 
But having finifhed the account of my experiments, I fhall 
finifh my letter, not daring to venture conjectures upon a fub- 
jeCt fo intricate in itfelf, and which is yet fo new, and upon 
which the ableft philofophers of the age feem to be fo much 
divided in opinion. 
