48 _ Correspondence—Mr. A. B. Wynne. 
tive. Again, in the case of metamorphic sedimentary rocks, we find 
one group which exhibits foliation very distinctly, another which 
does not. Now there is no name, so far as J am aware, for the rock 
in the latter group, which is the equivalent of gneiss in the former.' 
Again, unless we accept such a term as Hornblende rock (which 
I do not like), we have no name for the equivalent of Hornblende 
schist; and the same is true of other schists. Names like Halle- 
flinta, Hornstone, Lydian stone or Lydite, Porcellanite, want 
definitely fixing or deliberately leaving as indefinite—we have, in 
fact, no satisfactory nomenclature for the extensive group of compact 
felstone-like or flinty altered rocks. 
In the case of the igneous rocks, also, several points require 
settlement. The limits of the terms Quartz-felsite (or Quartz- 
porphyry, a name J much dislike), Quartz-trachyte, and Rhyolite 
require fixing. We have to consider whether we ought or ought 
not to separate the microcrystalline from the cryptocrystalline Quartz- 
felsites, and then to decide what are the essential characteristics of 
a Quartz-trachyte, what are the limits of the name Rhyolite, and 
what view is to be taken of devitrified rhyolites. At present, as it 
seems to me, there is no line drawn between some Quartz-felsites 
and Quartz-trachytes, other than geologic age, which I for one do 
not think a safe basis for classification. Again, assuming that we 
take crystalline condition as the basis of subdivision in our groups, 
separated at first by mineral (or chemical) composition, the 
meaning of the term basalt requires fixing, and the groups of the 
nepheline and the leucite rocks are very unsettled. The same may 
be said of the “mica-traps,” peridotites, and others, which, did space 
allow, it would be easy to name; but the above remarks may suffice 
to call attention to a real difficulty, which I imagine is widely felt 
by students of petrology. 
St. Joun’s CottEGe, Camp uiper, T. G. Bonney. 
November 20th, 1879. 
DR. WAAGEN’S VIEWS ON THE GEOLOGY OF THE SALT RANGE 
IN INDIA. 
S1tr,—With reference to part of my letter in your September 
Number bearing upon Dr. Waagen’s suppression of the Silurian 
group in the Indian Salt Range, I have since learned he has made 
the important admission: that for a time Stoliczka and himself were 
of opinion the fossils which I found in the Obolus group belonged 
to the Silurian period, and even now [May, 1879] he was “not 
prepared to maintain with certainty that that opinion was incorrect.” 2 
Notwithstanding this, in the case in point,? Dr. Waagen has not 
hesitated to condemn the classification adopted by me, although he 
elsewhere confessed himself uncertain of its being in error. 
A. B. Wynne. 
1 I have proposed that of granitoidite, Q. J. G. S. vol. xxxv. p. 322. 
* Neues Jahrbuch fiir Mineralogie, etc., 1879, ‘¢ Ueber einige strittigen Punkte in 
der Geologie Indiens. Dr. W. Waagen. Wien, 1 Mai, 1879.” 
3 Pal. Ind, Series xiii. Salt Range Fossils. 
