120 
THE GEOLOGIST. 
FOREIGN COllRESPONDENCE. 
By Dr. T. L. Phipson of Paris. 
Arsenic in Lignite and Bituminous Limestone, <kc. — Professor Daubree's 
Researches — Suhterraneaii Noises — The Oldest Fossil Mammalia — A 
New Fossil Saurian. 
Some years ago, M. Daiibree searched for arsenic and found it in 
many different kinds of rocks ; but more especially in the mineral 
combustibles belonging to different strata.* He found at that time 
that the tertiary lignite of Lobsaun (Bas-Rhiu), was uncommonly rich 
in arsenic : certain samples of this lignite were found to contain as 
much as from 0.002 to 0.008 of their weight of arsenic. 
These observations have just been confirmed by the same eminent 
geologist, under certain circumstances that deserve to be made known. 
A limestone stronglj^ impregnated with bitumen alternates with the 
lignite of Lobsaun. This limestone forms the principal element of 
the bituminous mortar {mastic) employed in the locality for different 
constructions. For some years it has been employed also to obtain 
certain pyrogenous oils, which are produced by a process of distil- 
lation. When the alembics which have been used in this distillation 
are taken down, the interior of the tube through which the oils distil 
is often seen to be encrusted with a curious deposit, produced by the 
gradual condensation, outside the furnace, of certain volatile sub- 
stances. This deposit, or sublimation, was found, upon examination, 
to be pure arsenic, crystallized in rhombohedi-ons ; it attains sometimes 
as much as two centimetres in thickness, and in the course of some 
months, it will completely obstruct the necks of the retorts. The 
arsenic thus deposited forms about the one-millionth part in weight 
of the rock which is submitted to distillation. 
The arsenic contained in the limestone is not entirely condensed 
in this manner ; a notable quantity distils over with the oils, as 
M. Daubree assured himself by a special investigation. In what 
state of combination the arsenic exists in these oils has not yet been 
ascertained ; it is well to be aware, however, that arsenic does exist 
in them, as they are constantly employed for burning in lamps, &c. 
The state in which this arsenic exists in the limestone of Lobsaun, 
has, however, been ascertained with certainty by M. Daubree, and in 
a very ingenious way. By the use of an appropriate solvent, the 
bitumen is dissolved out of the limestone ; then the carbonate of 
* See his Recherckes sur lapresence deVarsenic dans les Combustibles mineraux, 
dans diverses roches, et dans I'eatidela mer. (Annates des Mines, ^' s6rie, torn. 
xix. !>. (iG9.) An extract was also published in the Comptes-Rendus'de VAcad. 
de Sc. Paris, xxxii. p. 827. 
