Green-Mountain freeman. [volume] (Montpelier, Vt.) 1844-1884, 1873-06-18
agricultural.

CARBoNIC ACID IN THE SoIL.-It is well
known to every one, that plan Is derive much
OF their subsistence from the air about them
and that their principa articles of flod are
carbonic acid and water. The presence OF
large quantities of the former in the atrnos-
phere during tue carboniferous period of ge-
illogical history. caused the plants of that
time to attain great luxuriance and enormous
size. But plants fnd also supply of car
bonlc acid under the earth's surface the solid
earth being IN fact porous and permeated
with gas, OF which the quantity increases
with the depth of soil. De. Pettenkofet has
made some interesting experiments on this
subject in Munich. He first dug a pit four
teen feet deep. and in this he placed fine lead
pipes of one fourth inch diameter, and ending
at different depths. The first reached to the
bottom OF the pit; a second went to a depth
OF ten feet; athird about eight feet; fourth
five feet, and fifth two and one fourth feet
The upper ends of the tubes were carried
into the laboratory, and connected With as
piratOrs. After filling the pit with the earth
taken out, and pounding it firmly down, it
was found that air could be drawn through
all the tnbeS just as easily as if the tubes were
suspended in the open air. In the course of
from two and One-half to three hours. from
thirteen to sixteen quarts of air were drawn
through the tubes; and the amount of car
bonic acid was determined by absorbing it in
baryta water. Observations were made at
all seasons Of the year, and the quantity of
earbonic acid was found to be the greatest in
August and September, when from fourteen
TO sixteen parts OF this gas were found in one
thousand parts air from a depth of fourteen
ieet. The smallest quantity found at this
depth was IN January, when three and forty
SIX one-hundredth volumes of gas were found
In one thousand volumes of air. The air
nearer the surface contained much less of the
gas, except in the months of June and july.
The experlmenter thinks that this carbonic
acid may be produced by organic processes
in the soil, being given off by living organ
lsms OF a very low order The fact that the
amount decreases as we come nearer the sur
face is attributed to the diffusion of it into
the air, ventilation being less perfect in
summer than IN winter, as is the case in
dwelling or elsewhere. Nearly the whole
amount OF carobnic acid present in the at
mosphere, he thinks, comes from the soil.
1t Is noticed, by Schultze, in 1871, that when
the wind blew from the sea, the percentage
OF this gas in the air was less than when the
wind had travelled over the continent. Ros
coe established the unex pected fact that all
the furnaces and chimneys in busy Mancaes-
ter did not pereeptibly increase the amount
OF carbonic acid in the atmosphere of the
city; much less could the manufactures
scattered over the continent explain the phe-
nomenon observed by Schultz. The sup
position that it is everywhere given off from
the soil is the only plausible explanation OF
1t. We hope to hear of the experiments be-
ing repeated in different parts of our own
sountry, so that the results of different OBJ
servers may be compared. Scientific Amer
lean.