Rev. T. G. Bonney — The Lherzolite of the Ariege. 
59 
shale, apparently at a high dip, which the Carboniferous beds of the 
neighbourhood are not, traversed by several dykes of mica trap. 
These dykes are quite unlike anything eise in the country; but 
resemble similar dykes in the Kendal country, where they are never 
known to pierce the Carboniferous beds, but are exclusively confined 
to the Silurian rocks. The hardened shale traversed by fliese dykes 
in Teesdale is not unlike Skiddaw slate, which also was once 
similarly worked for slate pencils in Westmoreland ; but I cannot 
assert, merely after a short visit on a stormy Sunday afternoon 
in November, that the shale is not hardened Carboniferous shale, 
hardened by the dykes : but • the beds are as much like Skiddaw 
slate as Carboniferous shale, perhaps more so ; and this similarity, 
together with the apparent high inclination, and the Silurian 
character of the dykes, when taken along with the breccia at 
the base of Falcon Clints, leads one to ask the question at the 
head of this notice. 
V. — The Lherzolite of Ariege. 
By the Eev. T.- G. Bonney, M.A., F.G.S. ; 
Fellow and late Tutor of St. John’s College, Cambridge. 
T HE rock Lherzolite has been described by Prof. Zirkel in bis 
valuable Beiträge zur Geologischen Kentniss der Pyrenäen 
{Zeitschrift der Deutsch. Geol. GeseL, vol. xix. p. 68), but is generally 
passed over with the briefest mention or entirely omitted in English 
works on Geology. Even in Cotta’s “Bocks Classified and Described ” 
it is barely noticed, and the word is left out in the index. On this 
account, and seeing that, so far as I am aware, no description of its 
microscopic structure has yet been published, a notice, embodying 
the results of Prof. Zirkel’s paper, and of a brief visit of my own to 
this not very accessible locality, may be useful to students. 
Lherzolite is a crystalline aggregate of the minerals olivine, en- 
statite, and diopside, with some picotite, in texture varying from 
finely to rather coarsely granulär ; that from the locality visited by 
myself being, on the whole, of the former character. It obtains its 
name from the Etang de Lherz, a small tarn in the Eastern Pyrenees 
(Dept. Ariege), above Aulus, in the valley of the Garbet, 38 kil. 
from St. Girons, and near the Col d’ Erce (or Port de Lherz), an 
easy pass (5341') leading to Yicdessos in the valley of the Oriege. 
The rock entirely surrounds the Etang, and is the largest of a linear 
series of seven exposures in the vicinity of Yicdessos. 
The Etang de Lherz is a shallow tarn occupying apparently a true 
rock-basin, the longer axis of which lies roughly N. and S. The 
water escapes from the northern end by soaking tbrough some peaty 
ground. On the Western side is a tiny Island. The tarn is sur- 
rounded by rounded masses (probably once ice-worn) and fallen 
blocks of the Lherzolite, which also rises from the western shore in 
a craggy hill. A furlong or less from the eastern shore limestone 
shows tbrough the grass and Stretches away in that direction, formiDg 
the general mass of the country. The tarn is not in the line of the 
main valley of the Garbet, but in a sort of open upland glen, a little 
