G. H. Williams—Norites of the “ Cortlandt Series.” 148 
hematite, similar to those found in the well known perthite, or 
even in some crystals of carnallite. 
Although such inclusions are almost always present in the 
older rocks which have originated at great depths, they are by 
no means unknown in certain minerals of volcanic rocks which 
have cooled at the earth’s surface. Those above described in 
the plagioclase of the Cortlandt norite are almost identical in 
both form and disposition with the ones which Prof. Hermann 
Vogelsang so admirably figured in 1874 from the nosean of 
Rieden.*  Mierisch has also verv recently described and figured 
similar bodies in the sodalite and apatite found in druses of the 
limestone blocks ejected from Monte Somma.t + 
Although the norite is the prevailing type of massive rock 
throughout Cortlandt township, still the pure aggregate of 
plagioclase and hypersthene is comparatively rare. ‘In almost 
every case either biotite or hornblende or monoclinic pyroxene 
is present, and often two or all three of these together in acces- 
sory quantities, forming transitions to the mica-diorite and gab- 
bro which are common modifications of the same continuous 
mass, especially around its periphery. The writer has there- 
fore designated all rocks in which one-half or more of the non- 
feldspathic constituents was hypersthene as norite, and named 
varieties of this after the prevailing accesssory component. 
* Ueber die natiirlichen Ultramarinverbindungen. Bonn, Taf. I. 
+ Tschermak’s Min. und Petrog. Mitth., viii, pp. 166 aud 183. 
¢ The writer does not wish to imply by the above observations any direct oppo- 
sition to Professor Judd’s theory of schillerization. Through the kindness and 
liberality of this gentleman he has been enabled to study a suite of sections of the 
Scottish rocks upon which this theory was based, and can express himself as con- 
vinced of the correctness of Prof. Judd’s conclusions as far as these rocks are 
concerned. The idea of schillerization, which Prof. Judd has so admirably devel- 
oped, is to be welcomed asa new and most valuable addition to what microscopical 
petrography has accomplished. It is doubtless capable of a wide application and 
will serve to clear away many difficulties. The writer desires only to call atten- 
tion to the fact that it is unsafe to ascribe all the inclusions occurring in the old 
granular rocks to the effects of what Professor Judd calls schillerization, even 
when these apparently resemble such as have been undoubtedly produced in this 
way. How ofien is it observed that nature employs diverse means to accomplish 
approximately the same result! Two investigators, commencing with the study 
of effects which may with certainty be attributed to very different causes, often 
succeed in tracing these by insensible transitions toa common ground, where the 
phenomena observed may be ascribed with almost equal right to the one cause or 
the other. Here two opposing views may be defended with excellent reasons, 
which depend largely upon the direction from which the subject was approached. 
Both may be right and yet particular cases may arise where it is impossible to de- 
cide between them. 
Thus it would appear that both original and secondary inclusions may occur in 
the constituents of the granular, deep- -seated rocks and that the similarity between 
them may be so great as to occasion difficulty in referring certain cases to the one 
class or the other. 
