AND OF PLANTS UPON THE ATMOSPHERE. 
167 
Experiments concerning the influence of plants on atmospheric air mixed with va- 
rious proportions of carbonic acid ; the plants being exposed to the sun, and con- 
fined in jars containing from 600 to 800 cubic inches of air, and which rested 
upon mercury covered by a thin film of water. 
Experiment 1. 
Date. 
Circumstances of the experiment. 
Proportion 
per cent, of 
carbonic acid 
added. 
Absorption 
per cent, 
caused by 
solution of 
potash. 
Residuum 
per cent, 
after burning 
phosphorus 
in a portion 
of the air. 
Allowance 
for phospho- 
rus vapour. 
Calculated amount 
per cent, of 
nitrogen. 
oxygen. 
April 10. 
12 a. m. A small Cypress in a garden- 
pot was introduced into the jar, its 
stem being cemented air-tight into 
the hole in the two hemispherical 
iron plates, that fit the inner margin 
of the hollow cylinder 
0 
0 
81 
2 
79 
21 
6 p. m. After a cloudy and gloomy 
day, with only occasional gleams of 
sunshine 
0 
0 
81 
2 
79 
21 
April 1 1 . 
8 A. M 
0 
0 
79 
2 
77 
23 
8 i 
8 
8 
5 p. m. Stormy and cloudy day, much 
like that preceding it 
0 
0 
79-5 
2 
77-5 
22-5 
April 12. 
12 a. m. No sun during the morning. 
but a settled rain throughout .... 
0 
0 
81-5 
2 
79-5 
20-5 
1 P. M 
4 
4 
April 13. 
8 A. M 
0 
0 
82 
2 
80 
20 
12 a. m. A fine bright day, with oc- 
casional storms 
3 
3 
4 P. M 
0 
1 
79 
2 
77 
23 
April 14. 
The unfavourable state of the 
weather induced me to suspend the 
experiment. 
Remarks . — The circumstances most worthy of remark in this experiment appear to be, 1st, the emission 
of 2 per Cent, of oxygen the second day, when the proportion of carbonic acid in the air of the jar was too 
small to he detected by my apparatus ; and 2ndly, the absorption of carbonic acid afterwards when no 
oxygen was evolved. In the first case we must suppose that the plant had imbibed from the atmosphere, 
previously to its confinement, the carbonic acid, which under the influence of sunshine it decomposed within 
the jar ; in the second, that it absorbed a large quantity of carbonic acid, which in the unfavourable state 
of the weather it did not decompose. This latter supposition must be adopted as applicable to most of the 
succeeding experiments ; for my apparatus was proved to be sufficiently perfect to prevent any such escape 
of carbonic acid, within a corresponding period of time, introduced into the jar, when no plant was present 
in it, and thereby to obviate any suspicion that it might arise from a defect in the union of the joints. 
Experiment 2. 
April 19. 
2 p.m. A dull day, with a tendency 
to rain. Stem and branches of a 
Persian Lilac ( Syringa persica ) in- 
troduced into the jar in the manner 
above described 
9 
9 
81 
2 
79 
21 
April 20. 
7 P. M 
8 a.m. Air examined before the sun 
0 
2-75 
78 
2 
76 
24 
had acquired any power 
11 A. M 
7 p. m. After a dull day, with occa- 
sional storms until 2 p. m., when 
0 
325 
2-75 
6-00 
80 
2 
78 
22 
April 2 1 . 
the sun broke out 
Observed the leaves to be altered 
and faded, and this, together with the 
unfavourable state of the weather, in- 
duced me to discontinue the experi- 
ment. 
0 
4-25 
80 
2 
79 
21 
Observations . — It appears from this experiment, that when a plant is in a perfectly healthy and fresh 
condition, it may add considerably to the amount of oxygen even in dull weather. 
