THE NEWARK SYSTEM OF NEW JERSEY 557 
hard black shales are not ‘‘baked” shales. The most marked 
macroscopic changes induced in the altered shales are (a) a 
greater or less induration, (d) change in color,—the red shales 
in general becoming purple and then a blue-black or green near 
the trap, and (c) the development of secondary minerals, — 
very commonly epidote and tourmaline. Where the change 
has not produced definite crystal forms or nodules, an incip- 
lent segregation has often occurred, giving the rock a more 
or less mottled aspect, and on weathered surfaces a warty 
appearance, although this latter characteristic is not limited to 
the metamorphosed beds, but occurs in some layers of the Lock- 
atong beds far from any known trap. 
Of these three changes the third is believed to be the most 
significant. Mere induration or change of color do not neces- 
sarily signify ‘‘baking,” but when all three occur together and 
only in layers in close proximity to certain trap sheets, proved 
to be intrusive by their structural relations, the changes can be 
safely ascribed to the igneous rock. Many of the baked shales, 
on weathering, become a pale blue or ashy gray color, a tinge 
never taken by other layers. 
Metamorphosed shales occur both above and below the trap 
of Sourland Mountain and are well exposed in the bluffs near 
Lambertville. They are associated also with the Rocky Hill 
sheet, fine exposures being found along the canal near Rocky 
Hill village. In fact all the intrusive trap sheets are surrounded 
by shales which have been more or less altered in texture, color, 
and mineralogical constitution. Baked shales surely exist near 
some of the trap sheets, but all hard, black shales of the system 
are not baked, as was formerly supposed. 
Unclassified beds —It has been impossible to classify definitely 
the beds of a small area between Mount Airy, Lambertville, and 
the mouth of Alexsocken Creek. Their structure is complex, 
the dips vary greatly in direction and amount, and in many cases 
they are crushed and distorted. Two small masses of trap 
occur within the area, and some of the beds are certainly meta- 
morphosed. Whether they belong to the Lockatong or Bruns- 
