204 Scientific Proceedings, Royal Dublin Society. 
cyclonic type. Possibly this confirms Spring and Roland’s 
view, that stagnation of the air leads to a régime of maxima, and 
agitation to one of minima, but the evidence is by no means 
conclusive. 
This opportunity may be taken to mention v. Fodor’s figures 
as regards the effects of a rising and a falling barometer. 
According to him, in cold periods of the year, the carbonic 
anhydride increases when the barometer rises, and vice versd. ‘The 
reverse effects are produced in the warm periods. In support 
of these statements he gives the figures :— 
CO2 in 10,000 vols. air. 
JN 
Gan a 
Winter 1877-1879. Summer 1877-1879. 
Barometer rising, ; z 4:10 ; : 3°80 
A falling, : ‘ 3°78 ; : 3°95 
As regards the influence of temperature as a solitary factor, 
we believe that Petermann and Graftiau are the only observers 
who have investigated it minutely. According to them it is one 
of the four natural causes affecting the amount of the carbonic 
anhydride of the atmosphere, and they give the following figures : 
Temperature (C.), . —10to-5 —5 tod 0 to 5 5 to 10 10—15 
COgin 10,000 vols. air, 3°12 2-94 2°94 2°95 2°95 
Temperature (C:), < . . 15 — 20 20 — 25 25 — 30 
COz in 10,000 vols. air, . 2:92 Beeyil 2°88 
The explanation which they give is that cold abates the velo- 
city of diffusion of the carbonic anhydride from the lower layers 
of the air tothe upper ones. The inverse phenomenon is produced 
by elevated temperatures, and they recall the fact that Reiset 
obtained his minima during days of strong insolation. That 
frost augments the amount of atmospheric carbonic anhydride is 
also maintained by v. Fodor, who obtained the figures :— 
COz2 in 10,000 vols. air. 
Days before frost ; 3°54 
», introducing 5 é ‘ : 3°71 
»» during thaw : : z ; 3°69 
and explains them by assuming that frost drives the carbonic 
anhydride out of the ground; while, during a thaw the water, 
robbed of its gases by the act of congelation, will reabsorb carbonic 
