FOREIGN CORRESPONDENCE. 
105 
M. Elie de Beaumont, on presenting this letter to the Academy, ob- 
served that the persevering researches of Professor Sismonda cannot be 
too highly praised. Having lately visited the Col d'Encombres himself, 
he gave an interesting account of his recent excursion there, and ex- 
plained the position and structure of the beds indicated by M. Sismonda. 
These vary from 7 j to 1 0 or 11 feet in thickness ; they are covered by 
about 100 feet of calcareous strata, apparently devoid of fossil remains, 
and repose on a bed of grey crystalline limestone, presenting a few veins 
and blocks of black silica, which emits a bituminous odour when 
broken. It is very difficult to extract the fossils from these deposits, 
so firmly are they cemented together by the crystalline limestone. These 
beds of limestone have, however, completely escaped the metamorphic 
action which has so thoroughly modified the mineralogical characters 
of the surrounding strata. Erom this fact, and from the circumstance 
already mentioned of all the fossils of these three Liassic divisions being 
here distributed in one single bed, M. Elie de Beaumont is of opinion 
that the fossil beds of the Col d'Encombres will in future be regarded 
as one of the .most classical and remarkable of the Liassic formations. 
The second letter addressed to the learned Secretary of the Academy 
was from M. Eiviere, who is studying, in Prussia, the direction of 
the veins of zinc and lead ores. A short paper enclosed in it, 
and entitled, " On the genei-al direction of the veins of Blende and 
Galena,^'' contains the following results : On the right side of the 
Bhine, as the author has previously shown, the general direction 
of these veins (which are encased in the Grauwacke and Phyllades* 
of the country) is east 30° north, west 30° south. Towards 
the latter part of last year he found that the veins on the left 
side of the river not only show a similar nature and structure, but 
appear to have the same direction, as those on the right side ; of which, 
in fact, they seem to be a prolongation. M. Eiviere has also studied 
the same metallic veins in La Vendee, Auvergne, Forez, Ardeche, 
Cevennes, the Alps, &c., and now arrives at these conclusions : first, 
that there is a remarkable constancy in the mean direction taken by the 
veins of Blende and Galena throughout a great part of France ; secondly, 
that these veins run generally north-west and south-east, inclining rather 
to the west and to the east, and seeming to appertain to M. Elie de 
Beaumont's Systeme du Morbihan, which he has defined by a line to the 
* Clay-slate. — Ed. 
