242 The American Geologist. April, 1902. 
examination shows, however, that the original minerals of the 
granite are but little altered; and that it is essentially a case 
of the saturation of a rock along joints and rifts by the sec» 
ondary mineral of a neighboring rock. This appears to throw 
some light upon the problem of the quartzose chloritic rock of 
the Antwerp-Fowler iron mines, and at least suggests the pos- 
sibility that the quartzose portions of this matrix of the iron 
ore may be, after all, a phase of the granite. But the basic 
dike is still required as a source, alike of the impregnating 
chloritic matter and of the metallic contents of the formation, 
NOTES UPON THE MAUCH CHUNK OF PENN- 
~SYLVANIA 
By Joun J. Stevenson, New York 
Professor H. D. Rogers recognized two series in the Lower 
Carboniferous of Pennsylvania, which he designated as Ves- 
pertine and Umbral. Professor Lesley rejected these names 
and replaced them with the geographical terms, Pocono and 
Mauch Chunk. The latter term is inappropriate as the char- 
acteristic features, shown by the series at that locality, mark 
only a small area within northeastern Pennsylvania. The 
Mauch Chunk, in much of the northern area, is triple, shales, 
limestones and shales; a division faintly recognizable even 
around the southern and middle anthracite fields, well-defined 
further south in the Broad Top field, east from the Alleghenies, 
and especially distinct in northern Pennsylvania on the north- 
eastern part of the Allegheny plateau within Lycoming county. 
The lower shales are present throughout northern Penn- 
sylvania, becoming the Shenango shales of I. C. White in 
the northwestern counties, but they disappear in the southern 
counties, being absent in Maryland, east from the Alleghenies, 
while under the Laurel and Chestnut Hill anticlines they dis- 
appear before the Conemaugh river is reached. 
Traces of the middle or limestone division have been recog- 
nized even at the east end of the southern anthracite field; it 
is better defined in the northern field, while in the Broad Top 
area it is distinct. Its lower portion is persistent as far north- 
ward on the Allegheny plateau as northern Lycoming county, 
northwestward to beyond Lock Haven in Clinton county and 
