62 
Rev. T. G. Bonney — The Lherzolite of the Arieye. 
is represented to some extent, as in the last, in the paste. In this 
(in the last two cases) one can readily distinguish bright green 
fragraents of diopside and rather numerous black grains of picotite, 
apparently imbedded separately. 
This mass of Lherzolite is the largest of the seven exposures in 
the district, and according to Prof. Zirkel is about 1300 yards in 
greatest length. Three other masses lie near it along the line of 
the little glen of the Suc. The rest are near its junction with the 
Oriege, one being on the opposite bank near the village of Sera. 
All are in the Liassic rocks, and, except the last, are very near their 
junction witb the granite, which even here is at no great distance. 
It is also more coarsely granulär thau the rock at the Etang, and the 
breecia is wanting. Lherzolite also occurs near Portet d’Aspet, in 
the upper Yal longue (Castillon), and on the soutli side of the Col de 
Lurde, in the neighbourhood of Eaux Bonnes. The principal rock 
here is a limestone with ophite, i.e. greenstone, near it. I have not 
seen any of these. 
The rather compact condition of the rock, and the fact that the 
olivine is in some specimens rather green, and the diopside a little dull 
in colour, while the enstatite does not always exhibit its characteristic 
structure, makes it often very hard to distinguish the component 
minerals of the specimens from the Etang de Lherz. They are better 
seen, however, on a polished surface, and can be separated, as 
Zirkel suggests, by treating the pounded rock, first with hydro- 
chloric acid, and then boiling it with caustic potass. In my 
Pisani specimen from Sem, the minerals are much more easily dis- 
tinguished, as is the case also, according to Zirkel, in liis specimens from 
this locality. The composition of the Pyrenean Lherzolite is according 
to an old analysis (Zirkel, p. 140) : — Si0 2 =45'0, A1 2 0 S =1 - 0, CaO= 
19-5, Mg0=16-0, FeO=12 - 0, CrO=0-5, with a trace of MnO 
and loss=6 - 0. Lasaulx gives the analysis of a Lherzolite from 
Norway (Elem. der Petrograph. p. 338) : — Si0 2 =37'42, A1.,0 3 = 
0-10, MgO=48-22, FeO=8-88, MnO=0-17, NiO=0-23. H 2 0 2 =-71. 
The rock varies slightly in different parts around the Etang, 
both in grain and in preservation. I collected specimens chiefly 
from near the Southern end, and about half-way down the west 
side ; the most serpentinous specimens coming from the former. 
Mr. S. Allport, to whom I gave a duplicate from Sem, kindly cut 
me a beautiful slide from it, and I have had slides (six in all) 
cut from three varieties collected by myself at the Etang. I will 
refer to them as No. I. (from Sem [Pisani]), No. II. (specimen from 
the west side), No. III. (specimen from the soutli end), No. IV. 
(specimen showing a partial passage into Serpentine). This speci- 
men was cut close to a joint face where the cliange was greatest. 
Microscopic. Structure . — In all cases the rock is normally com- 
posed of olivine, enstatite, diopside, and picotite, with occasional 
minute specks and microlithic aggregates of an opaque black mineral, 
probably magnetite. Microliths of other minerals are rare. The 
first three minerals all occur in variable shaped grains ; those of 
the olivine roundish ; the diopside occasionally showing a slight 
