TACONIC SYSTEM IN MICHIGAN. 
101 
of the Taconic system. Yet in a region where igneous action has been so rife, and where, 
as has been stated in, the preceding pages, plutonic rocks are ready to meet the observer 
on all sides, it would not be safe to infer the place of any of the limestones without an 
actual examination. In this case I should have been right in locating the rock in the 
Taconic system without an examination; for only a mere inspection was required to see 
its identity with that at Camden, and its equivalency with that of Stockbridge, the special 
type of this species. I do not deem it at all necessary to repeat the characters of the rock ; 
but it is proper to say, that like the same mass at Camden, it has suffered by intrusive 
rocks. One of the quarries is traversed by a huge dyke of greenstone, which remains an 
upright wall about fifteen feet thick : its direction is N. 40° E. The slates in connection 
are the magnesian : their strike is northeast, with a curved dip to the southeast. 
YI. THE TACONIC SYSTEM IN MICHIGAN. 
INFORMATION FROM DR. DOUGLAS HOUGHTON, RELATIVE TO THE DEVELOPMENT OF THE 
TACONIC SYSTEM IN MICHIGAN. 
After the preceding pages were ready for the press, I received from Dr. Houghton the 
interesting information that this system is well developed in the State of Michigan. I 
give here the account which he obligingly furnished me of the rocks in question. 
The Taconic system is largely developed in the western and central parts of the upper 
peninsula of Michigan. The slates of the formation are finely exposed along the western 
boundary on the line of the Menomene river, which cuts across the formation. East of 
this, and near Lake Superior, the granular quartz makes its appearance in hills of an 
elevation of several hundred feet. This formation trends northeasterly, and probably in 
a direction nearly parallel with that in New-York. I am not furnished with details in 
regard to the separate, or subordinate masses. It is interesting to find the same rocks in 
so many independent fields ; and I may add, for the purpose of dispelling doubts in regard 
to the identity of the slates of the peninsula of Michigan and New-York, that on showing 
Dr. Houghton some of the flagging stones of the Taconic slate with fucoidal impressions, 
they were recognized at once as the same species of fossils he had observed in the slates 
of the Menomene river. Another fact stated by him is that he has observed many locali¬ 
ties where the slates of the Taconic system pass beneath the Potsdam sandstone, the 
oldest rock of the New-York system. It would be difficult to add to the weight of this 
testimony, in regard to the separate and independent existence of a system of fossiliferous 
rocks of an age anterior to the Silurian or New-York system. 
