302 
The American Geologist. 
May, 1895 
ores of northern New Jersey (American Geologist, vol. xii, p, 
25, 1893). 
In 1894 J. F. Kemp gave the following ascending order for 
the rocks on the eastern slopes of the Adlrondacks. At the 
bottom a series of quartz-orthoclase gneiss, sometimes con- 
taining hornblende or biotite or uugite, with plagioclases; 
secondly, a series of crystalline limestones closely' involved 
with black schists and gneisses, and lastly a series of intruded 
rocks of the gabbro family, penetrating both of the others. 
This order is noticeably similar to the parts of the Canadian 
Laurentian and upper Laurentian. 
It seems from the foregoing that, in respect to the existence 
of a crystalline terrane, alike in the Taeonic and the Adiron- 
dack areas, of similar composition and order of stratification, 
there is a general concord of opinion among those geologists 
who have paid special attention to the composition of the two 
areas. 
The succession of geologic events in the principal eastern 
areas may be seen in the following tabulation : 
1. Table of geologic features. 
Adirondack area. 
CORTLANDT AREA. 
Taconic area. 
1. Potsdam nandstone 
Unconformable over 
(a) Hypersthene rock 
(b) Crystalline lime- 
stone. 
(c) Schists associa- 
ted. 
(d) A quartzyte. 
1. Potsdam sandstone 
unconformable over, 
(a) Primary, consist- 
ing of a changed 
qnartzvte or gneiss 
(at "Whitehall). 
(b) Olenellus 1 i m e- 
stone and quartzyte, 
near Poughkeepsie.* 
2. Disruption of No. 3 
by hypersthene rock 
and allied basic eriip- 
tives. associated with 
granite. The former 
with titanic iron ore 
and phosphates. 
2. Rupturin<j of the 
Olenellus limestone 
and associated schists 
by f^abbro. Metamor- 
phism. Titanic iron 
ore. 
2. Tilting, folding and 
metamorph i s m o f 
No. 3. 
■*Prof. Dwight mentions both these (i. e. Potsdam and Olenellus 
quartzytes) near Poughkeepsie, but he does not describe their actual 
contact. (Am. Jour. Sci., (3), xxxi, p. 125.) 
