378 
EStTMEBATION OF STBATA. 
true, and independent of the progress of positive geology in 
other countries ; while the systematic names applied to any 
particular formation of America, are founded only on the 
supposed analogies between the formations of America and 
those of Europe. Kow those names cannot remain the 
same, if after further examination, the objects of comparison 
have not retained the same place in the geologic series ; if 
the most able geologists Jiow take for transition-limestone 
and green sandstone, what they took formerly for zechstein 
and variegated sandstone. I believe the surest means by 
which geologic descriptions may be made to survive the 
change which the science undergoes in proportion to its pro- 
gress, will be to substitute provisionally in the description 
of formations, for the systematic names of red sandstone, 
variegated sandstone, zechstein, and Jura limestone, names 
derived from American localities, as sandstone of the Llanos, 
limestone of Cumanacoa and Caripe, and to separate the 
enumeration of facts relative to the superposition of soils, 
from the discussion on the analogy of those soils with those 
of the Old World.* 
• Positive geography being nothing but a question of the series or 
succession (either simple or periodical) of certain terms represented by the 
formations, it may be necessary, in order to understand the discussions 
contained in the third section of this memoir, to enumerate succinctly 
the table of formations considered in the most general point of view. 
I. Strata commonly called Primitive j granite, gneiss, and mica-slate 
(or gneiss oscillating between granite and mica-slate) ; very little primitive 
clay-slate; weisstein with serpentine; granite with disseminated amphi- 
bole; amphibolic slate; veins and small layers of greenstone. 
II. Transition strata, composed of fragmentary rocks, (grauwacke,) 
calcareous slate, and greenstone . earliest remains of organized existence i 
bamboos, madrepores, producta, trilobites, orthoceratites, evamphalites). 
Complex and parallel formations; (a) Alternate beds of grey and stratified 
limestone, anthracitic mica-slate, anhydrous gypsum, and grauwacke ; (i) 
Clay-slate, black limestone, grauwacke with greenstone, syenite, transition- 
granite, and porphyries with a base of compact felspar; (c) Euphotides, 
sometimes pure and covered with jasper, sometimes mixed with amphibole, 
hyperstein, and grey limestone ; (d) I’yroxcnic porphyries with amygda- 
loides and zirconian syenites. 
III. Secondary strata, presenting a much smaller number of raonocoty- 
ledonous plants ; (a) Co-ordinate and almost contemporary formations with 
red sandstone (rothe todtes liegende), quartz -porphyry, and fern-coah 
These strata are less connected by alternation than by opposition. The 
