476 : 
GEOLOGY OF THE FIRST DISTRICTo. 
wacke and red sandstone, we perceive, contain organic remains ; the grauwacke imperceptibly 
blends with the granitines, sienites, and greenstones of the Highlands, The hornblende rock 
and its metalliferous deposits unquestionably pass into gneiss gneiss, is foliated granite. 
Where then are we to seek for permanent distinctions 
Science is, yet in its infancy. It is as yet difficult to say what rocks are primitive, what 
transition, etc., except where their superposition and fossils can be traced. Most of the rocks 
that we have been accustomed to call primary, and consider as old as the foundation of the 
world, are found to have been sedimentary rocks, and since modified and rendered crystalline. 
Mr. Nuttall was probably the first to suspect that the white limestone of Orange and Sussex 
counties was not a primitive rock, and that the rocks of the Highlands are of the same age. 
I must, however, object to his inference that the epochs of time indicated by stratification are 
imaginary, although in a limited sense I agree with him. 
I think few can examine this belt of limestone ia Orange and Sussex counties, and trace 
its metamorphoses from the blue and calcareo-siliceous limestones, and the granular quartz 
rock and potsdam sandstone variously modified, and their association with sienitic, granitic, 
and hornblendic aggregates, without being convinced that they are metamorphic rocks ; and 
that they have been brought to their present form by the agency of heat; and that this has 
given a sufficient mobility to the particles of the rocks, to permit them to obey the laws of 
chemical affinity and of crystallization. 
(b). Metamorphic limestones of the Highlands, of Orange and Rockland counties. 
This rock is the same in its general characters and imbedded minerals as the white limestone 
of Warwick. It forms long narrow belts associated with granite, sienite, hornblende and 
augite rocks, and some anomalous aggregates. Dr. Horton, to whom was confided the ex¬ 
amination of Orange county, describing this rock, says : f 
“ This rock has a distribution of some extent in the county. Beginning on the Hudson 
river, it is first observed half a mile northwest of Fort Montgomery. It is here several rods 
in width, and can be traced two miles northeast from the line of Rockland county. It here 
lies confusedly, the stratification indistinct, rising into short and broken ledges ; it is white, 
and everywhere full of plumbago, pyrites of iron, boltonite and serpentine ; so much so, that 
it can scarcely be recognized as a white stone. It is, wherever noticed in this vicinity, small, 
crystalline, and very hard for this rock. This stratum or bed takes the direction of the gra¬ 
nitic rocks, in. which it is embracedthe line of bearing being northwest and southeast 
nearly,” 
Local details. “ Proceeding from this point directly northwest, six or seven miles- along 
the gorge through which Fort Montgomery creek reaches the Hudson, we reach another bed 
of this rock. This point is a few rods northwest of the Forest of Dean mine. Here this 
* American Journal of Science, Vol. 5, p, 247, 248. f Third Annual Geological Report of. New-York, 1839, p. 139, 141, 
