216 Scientific Proceedings, Royal Dublin Society. 
to the production of bicarbonates, which are washed downwards). 
Finally, there follows a period during which the micro-organisms of 
decay are in full activity, and carbonic anhydride is produced in 
abundance. 
(7) Two other meteorological factors* intermittently affect ground 
air, leading either to its escape into the atmosphere or to its imprison- 
ment in the soil, namely, changes of pressure and of temperature, and 
vy. Fodor is of opinion that from these causes very considerable 
‘«‘streamings”’ of ground air occur. These streamings could, he 
thought, be best traced by a comparison of the amount of carbonic 
anhydride found in the atmosphere close to the ground with that at 
gome distance above it, and accordingly he systematically determined 
these amounts simultaneously (at 3-1 cm. and 24 m. above the 
ground, respectively) during three years (1877-1879). 
The conclusions at which he arrived from these determinations 
were as follows:—The carbonic anhydride at ground level is, during 
the greater part of the year, considerably in excess of that above the 
surface, and the variations in the former are much more considerable 
than those in the latter. Both imcrease and decrease at ground level 
precede those occurring in the higher layers of the atmosphere, and, 
in general, the fluctuations in the amount of atmospheric carbonic 
anhydride are mainly due to the absorbing action of the soil on the 
one hand, and the evolution of ground air on the other. 
Soil possesses the power of diminishing atmospheric carbonic 
anhydride at times, and then the air at its surface contains less than 
at higher levels. Rain causes this, especially in spring; and that 
thoroughly moistened ground is the factor leading to absorption of the 
gas is further shown by the circumstance that the carbonic anhydride 
in the air at ground-level is least at the end of winter and the com- 
mencement of spring—that being the period when the soil, and 
especially it upper layers, are wettest. 
vy. Fodor has plotted out graphically, in a series of curves, the 
diurnal variations in the amount of carbonic anhydride in ground air 
at two different levels, those of the atmosphere close to the ground and 
at some distance above it, as well as the variations of temperature, 
rainfall, &c., during his three years’ investigation. 
As his diagrams are somewhat complicated and unwieldy, we have 
taken the liberty of constructing from the data supplied by him two 
1 Tn addition to wind, which according to vy. Fodor displaces ground air by pure air, 
thus leading to an escape of carbonic anhydride from the soil. 
