398 
THE QEOLOGIST. 
beds, leaving those wlio desire fuller information to obtain it from the 
book itself, which offers an admirable model for the production of similar 
works in our own country. Such works on local geology are too few 
with us, and are generally too poor, both in ability and information, 
to merit regard ; it is most commendable therefore to promote the desire 
for this class of productions on every occasion that presents itself, and a 
better model for a simple geological sketch could not be taken than the one 
before us. 
The arrondissement of Montbeliard is situated at the extreme frontier 
of France, near the Vosges, in a depression which separates those moun- 
tains from the northern Jura. It consists almost entirely of the Jurassic 
formation ; but outcrops of the Triassic and masses of other rocks are how- 
ever met w ith. 
The Trias is divided into Gres higarre (variegated sandstone), Calcaire 
conchylien (Muschelkalk), and Marnes irisSes (Keuper). 
The Jurassic formation offers eight subdivisions — the Lower, Middle, 
and Upper Lias, the Inferior and Great Oolites, and the Oxford, Coralline, 
and Ximmeridge series. The base of the Lower Lias is a yellowisli-white 
quartzose sandstone, four to five metres thick, full of casts of Cardinia 
and other bivalves, and correspondiag to the Gres d'Hettanges. Over this 
follows the dark grey Calcaire a Giyphees arquees, attaining the thickness 
of ten to twelve metres. The Middle Lias presents, at its base, grey or 
blue marls and dark -coloured, marly, fragile limestones, slightly schistose ; 
these are the Marnes a Gryphaa cymhium. The second group is formed of 
blue limestone, disposed in nodules in regular beds, alternating with 
narrow beds of marl — Calcaire a Belemniies. The third group, the Ma?^nes 
a Ammointes marc/aritatus, consist of dark grey shaly marls. The Marnes 
a Plicatules, the fourth and last group of the Middle Lias, alternate with 
marly limestones. They are always micaceous and sometimes sandy. The 
thickness of the whole division is about thirty metres. The Upper Lias is 
divided into three groups, the Schistes hitumineux, the Marnes a Trochusy 
and the Gres supraliasique. The first consists of ver}^ friable, argillaceous 
schists, higbly impregnated M'ith bitumen ; the second are firm grey or 
whitish marls ; and the last is formed of nodules and fine layers of very 
friable sandstone, very micaceous, alternating with sandy clays charged with 
mica, and known as the Marnes micacees. The thickness of the division 
is from twenty to thirty metres. The principal fossils in the upper beds — 
Ammonites insignis, Schubl. ; A. primordalis, Schl. ; A. bifrons, Brug. ; 
Trochus duplicatus, Sow. ; Leda rostralis, Lam. sp. ; Nucula Hammerii, 
Defr. ; Astarte Voltzii, Hoen. The Inferior Oolite commences with red- 
dish or yellow limestones, enclosing regularly stratified beds of hydroxide 
of iron, the OoUthe ferrugineuse. Above this is the Calcaires a Entroques 
(entrochital limestone). Then, again, the Calcaires a Poly^iers, enclosing 
siliceous nodules. The thickness of this group, over forty metres in the 
Jurassic chains, is considerably reduced at the northern extremity of the 
arrondissement. The Oolitic iron is an excellent mineral, and supplies a great 
many of the factories of Franche-Comte. There are important mines in it 
worked by the Compagnie des Forges from Audincourt to Dampjoux, near 
the mouth of the Barbeche. The Entrochal limestone furnishes a building 
stone of very excellent quality, which is almost exclusively employed at 
Besan^oii by the military engineers. The Great Oolite presents three 
divisions constant in the Jura, but elsewhere artificial, and more distinct 
in their mineral character than by their faunas. These are the Marnes a 
Ostrea acuminata (Marnes vcsuhennes of Marcou) ; the Great Oolite, 
properly so called, and the Dalle nacree. The first is a blue marl, made 
