PALAEONTOLOGY OF NEW-YORK. 
and present on a more extended scale all the phenomena which have been 
described as occurring in localities farther south. In tracing the formations 
still farther to the north, the highly inclined, folded and contorted stra¬ 
tification of these shales, conglomerates, and limestones, gradually dis¬ 
appears ; the metamorphic condition declines in the same ratio ; until the 
strata assume nearly their normal condition and position, and exhibit 
unequivocally the characteristics of the Trenton limestone and the Hudson- 
river group. 
A similar change in the character of these rocks has been before shown, 
in tracing the strata westward from the Green mountain range ; in which 
direction the foldings and the metamorphism gradually disappear, till the 
rocks assume their normal condition. In Canada, however, this change is 
not to the west or the east of the trend of the metamorphic chain, but in 
the continuation of the chain itself to the northeast, and in the trend of 
its greatest elevation, disturbance, and metamorpliism; showing that all 
the phenomena exhibited in the Green mountain range are superinduced 
upon the rocks of the Trenton and Hudson river periods. Not only has 
the general identity been thus determined, but individual beds of the 
metamorphic belt have been traced in their line of strike till they assume 
their normal aspect. 
Nor have the investigations rested here : for the chemical examinations 
of Mr. T. Sterry Hunt (of the Canada Geological Survey) have shown 
that the unaltered beds contain the same mineral components, and in the 
same proportions, as do the altered beds. 
The great serpentine range of rocks, which are known to belong to the 
upper part of the Hudson-river group, have been proved to correspond in 
chemical character to the unaltered rocks lying in the same geological 
position, and identical with the continuation of these beds*. Geological 
structure, therefore, and chemical and palaeontological evidence all unite 
in proving the age of these deposits. 
* I need only refer in this place to the elaborate Reports of Progress in the Canada Geological Survey, 
and to the various Essays by Sir W. E. Logan and Mr. T. S. Hunt, for the proof in detail of what is here 
stated. 
