Pi s 5 ~ 
4 x 
G. H. Williams—Pyrowene and Hornblende. 261 
parallel growths of two original minerals, just as Rose at first 
xplained the occurrence of uralite."* That this may indeed 
the true explanation in some cases is most probable, but 
Tam convinced that in many instances it is insufficient. In 
1878 Dr. G. W. Hawes” figured and described an occurrence | 
side by side of augite and basaltic hornblende as an instance 
f paramorphism and the same interpretation was put two 
ears later by Professor R. D. Irving” upon similar cases occur- 
Mng in certain Wisconsin rocks. In neither of these instances, 
however, are the proofs of paramorphism adduced entirely con- 
Incing. Several cases therefore, recently noted by the present 
writer, where such a direct change of pyroxene to compact 
hornblende is admirably exhibited in every stage, seem worthy 
of a brief description. eg 
8S members of that remarkable group of massive rocks ex- 
sed just south of Peekskill, on the Hudson River, to which 
fessor J 
: They all consist largely of compact brown horn- 
blende, together with more or less augite and hypersthene and 
varying, though generally small propertion, of a basic feld- 
par, ° = . . - . 7 
_ Present. They were evidently all derived from one magma 
and exhibit very beautifully the structure termed by Fritsch 
and Reiss” “ Kutaxitic,” which is so commonly observed in 
acid lavas like trachyte and phonolite. All of these rocks 
Which contain pyroxene show the direct change of this mineral 
to compact brown hornblende in an endless variety of cases. 
T shall only attempt to describe one or two where this process 
8 Pogg a xxii, 1831. rp aid 
9 i i . . 
* Geology at Wisconsin ip. 170, 1880, Ck, Vanhise, this Jour, iI, 
This Journal, ITI, xx, p. 194, Sept., 1880. 
" Geologische Beschreibung der Insel Teneriffe, 1868, p. 414. 
