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Reports and Proceedings — 
of Hozemont and Grand-Pre is demonstrated to be a gabbro, but its 
relation to tbe other rocks is not known. On tbe other hand, tbe 
quartziferous porpbyry of Spa is undoubtedly intrusive, and so are 
tbe quartzose Diorites of Quenast, Rebecq-Rognon, and Lessines. 
As we liave binted at before, tbe nomenclature of crystalline rocks 
is becoming a matter of increasing anxiety to tbe geologist. Tbe 
present autbors are to be complimented on tbe simplicity of tbe 
System tliey bave adopted. One example will suffice : onder tbe 
term “diorite quartzeuse,” tbey designate a rock on wbicb tbe 
following names bave at various times been bestowed, viz. : 
Porphyrite, Zirkel. Porphyritic dialase, Naumann. Quartzose 
porphyry, Delesse. Oligoclase porphyry, Rotb. Chlorophyre, Dumont. 
Synonymy is an evil wbicb geology will sooner or later bave to 
deal with, botb as regards litbological and stratigraphical nomen- 
clature, and tbe sooner some broad rules are accepted by tbe majority 
of tbe leaders of tbe Science, tbe better. At present, in examining 
geological maps, or in reading geological works, half our time is 
wasted in finding out (if we do find out) wbat is meant by tbe 
terms used. Zoologists and Botanists are fortunate in baving some 
generally-recognized laws of priority, tempered to some extent by 
fitness, and it certainly does not appear wby Geology sbould con- 
tinue to lack any relief of a more or less similar cbaracter. — G. A. L. 
REPOETS .A.:CT:D PEOCEEEIUG-S. 
Geological Society of London. — I. — February 7tb, 1877. — 
Prof. P. Martin Duncan, M.B., F.R.S., President, in tbe Cbair. — - 
Tbe following Communications were read : — 
1. “On tbe Chemical and Mineralogical Cbanges wbicb bave 
taken place in certain Eruptive Rocks of North Wales.” By Jobn 
Artbur Phillips, Esq., F.G.S. 
In tbis paper tbe autlior described tbe felspathic rock of Pen- 
maenmawr, wbicb bas been erupted tlirough Silurian strata, and 
rises to a height of 1553 feet above tbe level of tbe sea. Tbe rock, 
wbicb is composed of crystalline felspar witb minute crystals of 
some liornblendic mineral, is fine-grained and greenisb grey, divided 
into beds by joints dipping north at an angle of about 45°, and 
again divided by double jointings, sometimes so developed as to 
render tbe rock distinctly columnar. At tbe eastern end of tbe 
mountain tbe stoue is so close in texture as often almost to resemble 
cbert. In tbe next two quarries westward tbe rock is coarser, and 
its jointing less regulär. In tbe most westerjy quarry tbe stone is 
generally fresber in appearance, closer in grain, and greener in 
colour. All tbese stones are probably modifications of tbe same 
original rock. From tbe cbemical analysis of tbe rocks tbe author 
concludes tbat, supposing tbem all to bave bad originally tbe same 
composition as tbe unaltered rock in tbe most westerly quarry, tbat 
at tbe extreme east of tbe mountain bas lost about 3 per cent. of 
silica, and tbe others bave received respectively an increase of 1-35 
