236 Le 3 IQOGUINAUL, (UT (AZ OILOG IZ, 
1. The white limestones are continuous with the blue limestones 
(now accepted as of Cambrian age) and every degree of transition may 
be found between them. 
2. Both have the same strike and dip. 
3. Both are conformable with a quartzite also containing Cambrian 
fossils. 
4. Both are unconformable with the gneiss upon which they rest. 
5. Both have in sum total the same chemical composition and are 
magnesian. 
6. The altered crystalline condition of the white limestone is due 
to the intrusion of igneous masses and to regional metamorphism, 
while the blue limestone never contains such igneous injections. 
7. The presence of certain minerals, especially chondrodite, is not 
indicative of geological age, as this mineral is known to occur in modern 
volcanic rocks. 
Westgate* holds that the crystalline limestones of Warren county, 
New Jersey, are distinct from and older than the blue Magnesian lime- 
stone, and of pre-Cambrian age, for the following reasons: They have 
a well developed crystalline character, and hold large quantities of 
accessory metamorphic minerals; they show no intimate association 
with the blue Cambrian limestones; they show no tendency to grade 
into them; they have been subjected to general metamorphic forces, 
of which the neighboring blue limestone shows no trace; they occur 
in intimate association with the granitoid gneisses, and in some cases 
appear to be interbedded with them. 
Grimsley’ describes and maps the rocks of a part of Cecil county 
in northwestern Maryland. The rocks are granite, diorite, and 
staurolitic mica-schist. The staurolitic mica-schist is regarded as a 
sedimentary rock. In this the granite-gneiss is intrusive, as shown by 
the fact that branching dikes and apophyses penetrate the adjoining 
schists and slates, producing pronounced contact effects upon them. 
The diorite occurs in dikes in the granite. 
@ RoVaNneeasE 
*The Age of the Crystalline Limestones of Warren County, New Jersey, by L. G. 
WEsSTGATE, Am. Geol., Vol. XIV., No. 6, pp. 369-379, December, 1894. 
?The Granite of Cecil County in Northwestern Maryland, by G. P. GRIMSLEY, 
Journ. of Cincinnati Soc. Nat. Hist., pp. 50, April and July, 1894. 
