Lerts & Bhake—The Carbonic Anhydride of the Atmosphere. 168 
(? organisms), whilst the relative proportion of oxygen has gone on 
increasing. “In the more remote geological ages there could 
have been no free oxygen at the high temperatures to which all 
combustible bodies were exposed, and we can only conceive the 
atmosphere when the earth had evolved sufficiently to have been 
composed of nitrogen, carbonic acid, and water. Such is the 
starting point of Koone’s doctrine . . . The next point to which 
the theory refers is that an immense amount of carbon is fixed in 
the earth by the remains of plants and animals, and never returns 
to the air . . . Oxygen alone remains in relatively larger and 
larger proportions . . . As for carbonic acid, it has almost 
entirely gone.” 
Phipson then describes his own experiments on the growth of 
plants in pure carbonic anhydride (and water vapour), and found 
that it did not kill them at once, but that they lived in it for some 
time. 
Then he exposed his plants to Keene’s primitive atmosphere 
(nitrogen, carbonic anhydride, and water vapour), and found that 
their vegetation was remarkably healthy and even luxuriant for a 
lengthened period. Next he argues that the primeval atmosphere 
consisted of nitrogen alone (and water vapour also ?), and that 
into this with the dawn of plant-life (which preceded that of 
animals) free oxygen first made its appearance in the atmosphere, 
and that since then plants have continued thus to pour oxygen into 
the air. As to the source of the carbonic anhydride from which 
the oxygen resulted he attributes it to volcanic action ‘“ which con- 
tinued to be intense until after the coal period, and appears to 
have gradually diminished from that period to the present time, 
though it is still very active . . . The oxygen of the atmosphere 
has thus gone on increasing in quantity from the earliest ages of 
the earth’s history until the present time; and when it had 
attained to a certain amount animal life became possible and duly 
appeared. At the same time carbonic anhydride has diminished, 
since the strata of the earth reveal immense deposits of carbon 
which was originally present as carbonic anhydride.” 
Meunier,! in criticising Sterry Hunt’s theory, is of opinion 
that the chief permanent source of carbonic anhydride evolution 
1 Meunier, Compt. Rend., 87 [1873], p. 541. 
