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Mineralogy and Geology. 121 
It would be a difficult task at this moment to fix precisely the number 
of these successive creations of animals and vegetables ; but science is 
every day leading us nearer ie ait result, although it requires more 
detailed facts to enable us to r 
At certain epochs, ho BS aa ‘changes in the physical state of 
our planet have fee folloy “— ots modifications equally great in the na- 
earth, and its climate, at these different epochs, iiesciitee of the his- 
tory of the formation of our globe. 
From the most remote historical times, the vegetables Ee our 
gobs have undergone no change. This is proved by the comparison 
ins and. plants preserved in the tombs of Egypt, with thaws whisk 
bes grow in that country. 
ntrary, the plants of the latest geological periods,—those 
1 rth before the last revolution of ie surface, and 
e enclosed in the “pags its named tertiary formations, 
—differ very considerably ons such as now grow in these same places. 
ground, are greater as y occur in the more ancient beds of these 
tertiary formations. “The most. facdee indicate a climate differing ghee 
from that of temper. erate Europe; the most ancient announce a warm 
ate than now occurs in atta region. 
But in all these beds, which are very recent when compared with 
the other parts of the crust of the globe, we find vegetation, as a whole, 
agreaine in all its principal features with the mass of the vegetable 
gdom which still inhabits the surface of the earth; there are the 
same classes, the atural families, often the same genera. ‘The 
general gharacters of this extinct vegetation are the same as those of 
the existing vegetation, and we mig t suppose ourselves merely trans- 
ported to another quarter of the globe, Viewed as a whole they are the 
same ; the details only are different. 
But if, on the contrary, we descend more deeply into the layers com- 
posing the earth’s crust, and go back to the more ancient periods of the 
creation; if we consider the vegetables preserved in the formations 
named secondary, which have preceded those of which we have spoken 
by many ages, we shall find the vegetable kingdom reduced to a m 
oa number of those natural groups which we name fe 
This variety of form and aspect, which mes such a charm 0 the 
existing vegetation, did not then exist; and, cha eee oe word 
the vegetable ki ingdom of those re cia acioa, we may say that the 
plants composing it, _ "tae varied and numerous jo Bow 
covering our ground, were all deprived of what ir greatest 
Szconp Srnixs, Vol. VI, py 16, July, 1848. aa 
