262 Marcel de Serres on the Old World 
Nore 10. M. Biot’s observations on the twilight, have proved 
that the height which has been rashly named as the limit of the 
atmosphere is much too great. As luminous phenomena may be 
produced independently of oxygen, Poisson inclined to believe that 
aerolites became inflamed much beyond the last gaseous strata of 
our atmosphere. But this departnient of science, like that occupied 
with the larger bodies composing the solar system, presents no solid 
foundation for our reasonings and researches, but that to which cal- 
culations and geometrical measurements can be applied. In like 
manner the atmosphere of the sun is confined, as M. de Humboldt 
has observed, to much more restricted limits than those to which the 
zodiacal light extends. 
Norte 11. Fourier, the inventor of the theory of heat, has inferred 
from the whole of his researches, that the temperature of the in- 
terplanetary spaces was about 60 degrees below zero. M. Liais, de- 
sirous to verify the observations made before his time, has found it 
necessary to lower still further the figure given by Fourier, and that 
the heat of these spaces approached to — 100°. Observations have 
been always found to agree with the hypothesis of a very low tem- 
perature. Thus MM. Barral and Bixio observed, in the ascent they 
made from Paris on 27th July 1850, that the barometer was at 
0m,33805, and their thermometer sunk to — 85° and even to 
— 39° 67, when they reached a height of 6512 metres. On the 
other hand, during a voyage undertaken in search of Captain Ross 
in the Icy Sea, the thermometer fell below — 56° 6, which may afford 
us an idea of the low temperature of the interplanetary spaces. 
Notre 12. We cannot cast our eyes on the crust of our globe, 
without observing marks of a destroyed organic world, The sedi- 
mentary rocks present a succession of organized beings, associated 
in groups, the greater part of which have disappeared and been re- 
placed by others. As this phenomenon is renewed at many inter- 
vals, the superimposed beds, from one to another, reveal to us the 
fauna and flora of different epochs. A profusion of organic forms 
has predominated, at all periods of the earth, in the basin of the 
ocean ; it is there that life has had its chief abode both in the ancient 
and modern world. The infusorial fossils of the cretaceous formations 
and of the fresh water tertiary, show us the immense development 
life had acquired in these ancient epochs. Thus, the tripoli of the 
last formations is almost entirely composed of the skeletons or 
carapaces of microscopic animals. M. Ehrenberg calculates that 
each cubic inch of this substance, weighing about 220 grains, con- 
tains forty thousand millions of Gallionella distans, which gives 
about 187 millions to a grain. At each friction of the stone, there- 
fore, many millions, perhaps ten millions of entire fossils, are re- 
duced to powder or atoms. On the other hand, the sand of the 
Antilles contains more than 3,840,000 infusoria in 30 grammes. 
The dust we trample under our feet is also filled with these infinitesi- - 
