_ 
Eas ere 
compared with the New World. 251 
singularly favourable to the vegetation of primitive times, 
while it in some degree arrested the development of air- 
breathing animals, which ‘had scarcely begun to show them- 
selves. After the appearance of life, fishes were the: only 
vertebrates which animated our earth; but these animals 
only breathe air dissolved in water, richer in oxygen than the 
atmospheric air itself. . 
. Now, that the atmosphere contains a much greater quantity 
of vital air than during geological eras, the species which 
breathe air are as common in nature as they were formerly 
rare. It may almost be said that the arrival of Man has for 
ever fixed the constancy of the proportions of carbonic acid 
in atmospheric air; at least they do not appear to have 
varied since that event. 
Vegetables also found a new cause of development in the 
carbonic acid which voleanoes, then more numerous than 
now, diffused through the atmosphere. . These striking phe- 
nomena, moreover, supplied them with abundance of ammo- 
niacal salts, which contributed in a powerful manner to im- 
part to them a vigour which has never been surpassed. 
If we compare primitive vegetation with the flora of ex- 
isting times, we shall soon perceive that none of the species 
which. characterised it are like our living races ; they merely 
present some analogies to the plants of islands now situated 
in the warmest and most humid regions. Are we not, then, 
authorized to regard this. double circumstance as a manifest 
proof of the influence which an elevated temperature, and, 
_ at the same time, a considerable humidity must have, exer- 
cised on primitive vegetation ? 
Little doubt will be entertained on the subject, wtints we 
ponsidder that the same fossil animals and plants are spread 
from Spain to the polar circle, and from South America as 
far as Australia and Van Diemen’s Land (See Note 6). 
Therefore, the same vegetables, embedded in coal formations, 
have in former times lived simultaneously in the two hemi- 
spheres, as well in the torrid zone as under the ice of the 
poles (See Note 7). 
From these facts, we infer that the heat must then have 
