GEOGNOSY AND GEOLOGY. 143 
than in the bottom series, decreasing with the distance from the latter. 
Conglomerates and sandstone are met with more abundantly, and alternate 
with masses of marl, with occasional beds of clay interposed. The strata 
are generally more extended than in the bottom series, and saddle and 
trough formations are of more frequent occurrence. 
The middle series, although often existing at considerable heights, more 
generally occupies the less elevated parts of mountain masses. It is 
deposited, either conformably or non-conformably, on the bottom series, in 
the former case passing as gradually into the bottom rocks, as it is sharply 
distinct in the latter. 
Organic remains are found in most members, sometimes existing in such 
quantity as to have furnished the principal matter of the strata. The 
greater number of these remains belong to extinct creations, the more 
recent strata alone exhibiting forms bearing an afhnity to the present. 
The middle series is divisible into a primary, secondary, and tertiary. 
Primary Middle, or Transition Rocks. 
A portion of the paleozoic group of Elie de Beaumont belongs 
to this division of our subject. The primary middle separates the 
bottom series from the floetz, in external appearance having much in 
common with the former. The more recent transition strata incline 
still more in character to the floetz. |The strata are more oblique in 
the vicinity of the bottom series than at a greater distance. Conglo- 
merates, with a cement frequently crystalline, alternate with purely 
chemical products of an imperfectly crystalline or amorphous character. 
Limestone occurs more conspicuously in the newer beds. This is 
sometimes in the form of marble and dolomite; found more abundantly, 
however, in that of limestone and compact magnesian limestone. Carbon 
is found partly pure, as in anthracite and graphite, and partly combined with 
oxygen and hydrogen as coal. Metallic minerals occur, but in less 
abundance, than in the bottom series: of metals there are gold, silver, 
copper, and mercury ;—of metalloids, arsenic and antimony ;—of ores, 
galena, sulphuret of iron, magnetic pyrites, copper pyrites, zincblende, red 
silver ore, glance antimony, grey copper, and cinnabar ;—of oxydes, 
specular, red, brown, and magnetic, iron ores ;—of metallic salts, principally 
spheerosidrite, and electric calamine. These occur in beds and nests, as 
also in veins, the latter sometimes of great extent. |The number of fossil 
remains increases with the distance from the bottom series; plants make 
their appearance in the more recent transition strata, as in the anthracite 
coal measures, which bear the impress of a damp insular flora. Decided 
cotyledons are not yet found; acotyledons, however, exist in abundance. 
Two formations may be distinguished: the transition slate, and the 
carboniferous. 
Transition-slate Formation. It is this formation which most nearly 
approximates to the bottom series, so as to exhibit an insensible gradation 
573 
