IS 
and certainty as our present knowledge of the subject 
will enable us to attain. 
223. It will be seen, as we proceed in this discus- 
sion, that our opinions on this subject are by no 
means so novel as they have been commonly sup- 
posed, nor as we ourselves, at one time, thought 
them to be; and we shall gladly introduce the opi- 
nions of preceding writers, not only because they 
must add weight to our own, but because we are 
anxious to do entire justice to those who have gone 
before us in investigating this much controverted 
subject. 
224. The experiments which have been detailed 
in the former part of our Inquiry (31. et seq.), and 
which were designed to prove the complete conver- 
sion of oxygen gas into carbonic acid by vegetation, 
were repeated a great number of times, and with e- 
very attention to guard against fallacy, which our 
own experience, and that of many friends who wit- 
nessed their progress, could suggest. In a subse- 
quent repetition of these experiments, we varied the 
mode of analysing the residual air, by first raising 
the jar, and then passing the alkaline solution (32.) 
which contained the carbonic acid, into a tube filled 
with mercury, and inverted in a trough of that fluid. 
To this solution, a portion of diluted acid was then 
added, which excited a brisk effervescence, and cau- 
sed the disengagement of more than two cubic inches 
of carbonic acid gas. On comparing the volume of 
this gas with the diminution which the whole air had 
suffered, we found it to be nearly equal ; so that we 
thus obtained, in a distinct and palpable form, a bulk 
