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ANNALS NEW YORK ACADEMY OF SCIENCES 
relations by several of those who have investigated the geology of the region. 1 
The stratigraphy depicted in these sections indicates the influence of the 
then prevailing opinion that the rock is of sedimentary origin. In the 
light of the evidence obtained in recent years, tending to prove its igneous 
origin, these sections would now, doubtless, be considerably modified. 
The object of these notes is to describe certain rock specimens and 
minerals collected during the past year and to discuss their characters and 
the conditions under which they were found to occur, together with any 
stratigraphic significance that may attach to them. 
I am indebted to Dr. Charles P. Berkey for the preparation of their 
sections for microscopic examination and to Dr. A. A. Julien for their criti¬ 
cal study, the results of which will be given in the next communication of 
this evening. 
The rock is everywhere extensively fractured and is traversed by what 
is apparently a uniform system of jointing, which coincides in general with 
the trend and slope of the hills and simulates more or less closely the features 
of strike and dip in sedimentary rocks. Deductions based upon these 
features alone would justify the opinion that the rock might represent a 
metamorphosed series of sediments and the area are inclined anticline, 
with a dip approximating 90 degrees in places along the eastern and southern 
escarpment and 45 degrees or less throughout the northwestern slope. 
The system of jointing is best defined in the vicinity of Bichmond, 
where the rock is denser, less weathered and more uniform in texture than 
it is at the northeastern end of the hills. In the latter region the major 
system of jointing is almost obliterated by innumerable fractures and shear 
planes and evidences of squeezing, slipping and shearing. It is here also 
that there is the greatest variation in the rock and the greatest number and 
variety of minerals. 
Where the rock is weathered it is soft and yellowish in color. It con¬ 
tains considerable iron, in the form of magnetite and chromite, which, in 
the process of weathering, become oxidised into limonite. The soft yellow 
phase of the rock, accompanied by local depusits of limonite, is best seen 
at the northeastern end of the hills, where the glaciation was limited, and 
over the unglaciated area on Todt Hill. At the southwestern end, where 
glaciation was more pronounced, the upper, weathered zone was eroded, and 
the rock is hard and dense in texture and dark green in color. 
Probably the finest series of rock specimens and characteristic minerals 
1 Cozzens, Issachar. "A Geological History of Manhattan or New York Island, etc.” 
Plate 4, “ Section of Staten Island from the Telegraph to the Kills.” 1843. 
Britton N. L. “ On the Geology of Richmond County, N. Y.” Annals New York 
Acad. Sci., Vol. II, Plate 16, section C. D. 1882. 
