TACONIC SYSTEM. 
143 
stated above. Varieties of these two often resemble each other; their connection, however, 
furnishes means for distinguishing them ; besides fossils are not unfrequent in the latter, even 
in the denuded strata, but more have been met with in the former. 
I have now stated what appears to be essential in discriminating correctly the limestones 
and slates of the systems of rocks which lie in such close proximity to each other. I believe 
them to exist in nature, and worthy of consideration. 
