TRANSLATIONS AND NOTICES 
GEOLOGICAL MEMOIRS. 
On the probable Eruptive Origin of several Kinds of GNeEtss and of 
Gneiss-GraniTE. By Prof. C. F. Naumann. 
[From Leonhard and Bronn’s Neues Jahrbuch fiir Mineralogie &c., Jahrgang 1847, 
3tes Heft. | 
Ir is particularly satisfactory to find, that at length opmions have 
been expressed by English geologists respecting a mode of formation 
of gneiss and foliated granite, which may have the effect of restrict- 
ing within just limits the hypothesis of the metamorphic origin of 
these rocks; an hypothesis which certainly met with a remarkably 
ready adoption, and which has been very extensively applied. It is 
at least to be hoped that the geologists of Germany will now give . 
some attention to these views, coming to us, as they do, from the other 
side of the Channel, sanctioned by so high an authority as that of 
Mr. Charles Darwin. 
The hypothesis that gneiss and similar rocks are in all cases only 
altered sedimentary deposits, is founded essentially on the parallelism 
in their texture and structure, and on their being frequently found 
interstratified with clay-slate, grauwacke, and other sedimentary 
rocks. It has been assumed as an undoubted axiom, that all such 
parallelism of structure must have resulted from sedimentary depo- 
sition, and this axiom has been applied far too generally,— Multa 
jiunt eadem, sed aliter. There were not wanting, in truth, examples 
enough of rocks with a remarkable parallelism of structure, as to 
which no one could assert that they were of sedimentary origin. I 
will not advert to the numerous and well-known examples of vesicu- 
lar lavas and amygdaloids, in which the flattened and elongated vesi- 
cles are arranged in parallel lines, although these afford the most 
striking proofs of the origin of such parallel structure; but I will 
take leave to call to the recollection of the reader some other cases 
of this nature. 
In the classical description of Piperno, which Leopold von Buch 
VOL. IV.—PART II. B 
