Lerrs & Bhaxke—The Carbonic Anhydride of the Atmosphere. 208 
in this connection the results obtained by a method like Petten- 
kofer’s are of far more service than those of methods like Reiset’s 
and Miintz and Aubin’s, where air passes into the absorbent during 
several hours. 
Petermann and Graftiau give the following figures concerning 
the effects of pressure in relation to the amount of atmospheric 
carbonic anhydride :— 
Height of Barometer in mm., 720-730 730-740 740-750 750-760 760-770 
Vols. COz in 10,000 of air, . oll 2°94 2°93 2°95 2°93 
Whence they conclude that pressure is without influence, except 
with extraordinary depressions when the amount increases. 
Spring and Roland give the following summary :—— 
Height of Baro- | mie i 2 Peres oe ts 
Sees 730 135 TON 45 750 755 760 765 770 
Hols C02 im).o gre) a: . 
10,000 of air, | 2476 3116 3-492 3-198 3-230 3-356 3-460 3-638 3-821 
from which it appears that the quantity increased steadily with 
increase of pressure from 745-770 mm.; but the effects at lower 
pressure are not so obvious. 
We have examined the tables of Reiset’s results, and find only 
two observations corresponding with a barometric height below 
730 mm., and in both of these he found a low amount, viz. 2:943 
and 2°955, and even taking into account the five occasions when 
he records “‘ tempests,” the mean is 2°944, which is below his 
general mean, 7. e. 2°962. 
It must be recollected that Reiset’s observations were made 
practically at the seaside, whereas those of Petermann and Graftiau 
were made well inland, and it is possible that this difference of 
locality may account for the discrepancy in the above results. 
We have also examined the (British) synoptic charts for 1879, 
on the dates of Reiset’s maxima and minima (above 3:05 and 
below 2°875 respectively) to ascertain whether any distinct con- 
nection could be traced between the type of weather prevailing at 
Dieppe and the amount of atmospheric carbonic anhydride there, 
but without much success. 
Of the sixteen minima, nine correspond with the cyclonic type 
of weather, and seven with the anti-cyclonic ; while of the eighteen 
minima, ten correspond with the anti-cyclonic, and eight with the 
SCIENT. PROC., R.D.S. VOL. IX., PART II. Q 
