354 Answer to Observations 
From which I infer that he imagines I was unacquainted with 
any of the six authors alluded to: but in this as well as several — 
other particulars he labours under a mistake. | bad consulted 
*¢ the ill-digested experiments of Dr. Ingenhousz,”’ the excellent 
and truly valuable volumes of Mr. Ellis, and the still more recent 
publication of Sir Humphry Davy; nor was I quite ignorant that 
Saussure, Scheele and Sennebier had entered the list of disputants 
ou this controverted subject. But should your correspondent 
ask, Then whv advance opinions in opposition to the ‘* old story 
of the purification of the atmosphere by vegetation, which had 
been treated of by others??? I would answer, that although 
the opinion is old, it is neither forsaken nor abandoned, nor is 
At left to sink without a powerful support to rescue it from obli- 
vion: for, notwithstanding W. H.-G, marshals the name of that 
truly excellent philosopher Sir Humphry Davy in the list of the 
half dozen who have opposed the old story of Dr. Priestley, 
and who he says have so /ong anticipated my opinions, I have 
no doubt but that, with all my “ unpardonable ignorance,”’ I 
shall be able to prove that he has been most egregiously mis- 
taken. [ will not retort his own language on Mr. W. H.G., 
but content myself with remarking, that from the diversity of 
opinions displayed in the above authors, it was not very unna- 
tural that I should entertain a wish to investigate this contro- 
verted subject, and particularly as | thought many of their de- 
tailed experiments were not unexceptionable. For example; 
who can approve of the effects of detached leaves while con- 
fined under pump-water being brought forward as a proof of 
the effects carried on by an entire and living vegetable while 
exposed to air? In my experiments I endeavoured to obviate 
objections of this nature :—how far I have succeded, I shall leave 
to others to determine. One of the motives which induced me 
to commit their results to your Magazine, was, that during my 
last course of lectures I was informed by a gentleman attending 
the lectures of the Surrey Institution, and who was present at 
my lecture on vegetable chemistry when I introduced some of 
those experiments, that the then chemical lecturer at that Insti- 
tution had promised to prove that vegetables improved the at- 
mosphere, but that he had not made good his promise or even 
attempted it: on which several gentlemen who were present, ob- 
serving that the experiments militated so materially against the 
popular opinion, expressed surprise that I did not make them 
public. Under these circumstances I communicated them to 
your Magazine.—But to return to your correspondent, who says, 
‘* Dr. Priestley was the person with whom the old story origi- 
nated; but that even he seems afterwards to have been aware of 
the inaccuracy of his conclusions :” for hé says in vol. iii. p. 273, 
; “* In 
