5.
If, then, the great general mean of normal atmospheric carbonic acid
deviates but little from 2.9 or 3.0, it is not doubtful that under local
conditions, in closed places, and under exceptional meteorological
conditions, considerable variations may occur in these proportions. But
these variations do not affect the general laws of the composition of
the atmosphere.
There are two entirely distinct points from which the measurement of the
atmospheric carbonic acid may be contemplated.
The first consists in considering it as a geological element which
belongs to the gaseous envelope of the earth in general, and it leads us
to express the general relation of carbonic acid to the quantity of air,
as about three volumes in 10,000.
The second, which relates to accidental and local phenomena, to the
activity of man and beast, to the effect of fires and of decomposing
organic matter, to volcanic emanations, and finally to the action of
clouds and rain, permits us to recognize the changes which can occur
in air exposed to the influences mentioned, and to a certain extent
confined. Without denying that it is of interest from a meteorological
and hygienic standpoint, it does not take the same rank as first.
Pages:
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166