Jk, diex. Brongniart sur les caracteres Loologiques, &c. 215 
does evidently oppose it?” M. B. ade ots t 
pinion.—He first shews that rocks ver 
same a though very different in n character. On he : 
all the organic remains imbedded in them are 
analogous, and have the common character of the gene- 
es which cause changes i in the mineral — 
Not so with those, which 
alter the generations iving beings; their action is ex- 
tended through a long course of ages, and their influence 
_ is scarcely perceptible from one age to another. Plants 
' and animals have scarcely varied their characters since 
the earliest periods of history. The geological characters 
erived from analogy of fossils are therefore more perma- 
bent, and of course of more value in determining the pe- 
riod of formation, than characters simply mineralogical. 
Of these, that from the nature of the rocks is the weakest 
—those from the relative height of the formation, the 
depth of its ravines, &c., and the — of — are 
nore important; but these may be pro by sudden 
na pg like the earthquakes of Calabriaswhich have 
changed the order and direction of strata, making hori- 
zontal perpendicular, and vice versa; and throwing recent 
fo tions apparently below the base of the more 
cient. The apparent relative height of formations is a 
delusive character, but their real relative height is essen-— 
tially important, se still less so, than that from analo- 
i of es There are some caus es of error, even in 
imate 
ies, and 
tain sper 7 olutions of 
globe, and have lived in different periods, and hence they 
are found in distinct formations—and species belonging to 
earlier formations, may by the abrasion of these formations 
have been mi ixed and imbedded in formations of a mueh 
hearer peri s 
S. 
ange 
