Lerts & Buaxe—The Carbonic Anhydride of the Atmosphere. 215 
decay. Fleck obtained, among others, the following analyses of 
ground air :— 
Grounp Arr From Deprus or St1x, Four, anp Two Merrzs. 
6 Metres. 4 Metres. 2 Metres. 
Minm. Maxm. Minm. Maxm. Minm. Maxm. 
Cox Cor: COs. COr (COp- CO,. 
Oxygen, . 5 6 14°94 14°85 15°67 16°79 16°38 19-39 
Carbonic anhydride, . 4-22 7:96 4-11 5-56 2°99 Ail 
19°16 22°81 19-78 22°35 Gey 22-30 
(2) More carbonic anhydride is found in the ground air from 
lower than from higher levels. 
(8) The amount of this gas at both levels has a definite connection 
with the seasons, increasing during spring and summer, reaching a 
maximum in July or August, then diminishing and remaining more or 
less stationary during the winter months. These effects are, as might 
be expected, due to temperature variations, the curve showing the 
temperature changes at the surface, corresponding on the whole, with 
those showing the variations of the carbonic anhydride of the ground 
air. 
(4) The variations in the amount of the carbonic anhydride of the 
ground air at lower and higher levels correspond with each other, but 
the curve is steeper in the former than in the latter. 
(5) The amount of carbonic anhydride in the ground air is related 
to the nature of the soilin two ways, depending (a) on its porosity, 
and (b) on its organic matter. The less porous a soil the greater the 
amount, and vice versd. This is no doubt due to the obstacle the first 
imposes to diffusion of the gas, while with a porous soil it readily 
escapes, and does not accumulate. As regards the organic matter, the 
greater its amount in a given soil the higher the proportion of carbonic 
anhydride in the ground air. 
(6) Rainfall has a marked influence on the amount of the carbonic 
anhydride of the ground air, and y. Fodor is of opinion that three 
distinct effects may be traced to it. First, the pores of the soil are 
sealed, thus offering an obstacle to the escape of ground air, and 
causing an accumulation of carbonic anhydride. This latter is then 
absorbed by the mineral constituents of the soil—(leading, we presume, 
