Perry.] 



342 [December 18, 



somewhat slaty in its structure; that it lies in the lower portion of the 

 Champlaiu slope of Vermont, and dips gently to the east. In all 

 localities it has been rauch eroded, what remains seeming to be only 

 a small fragment of the original formation; at various points, indeed, 

 it has been very largely cut away; while, in not a few cases, the beds 

 have been, to all appearances, entirely removed. For these reasons, 

 and on other accounts, it may be well likened to a reddish or cream- 

 colored ribbon, stretcheil along the western limits of the State, almost 

 eveiy where gnawed, its edges being in most places deeply eroded 

 and indented; while we find constant evidence that it has been in its 

 whole length terribly eaien into, and in parts altogether worn away. 



As early as the year 1847, perhaps it was somewhat earlier. Prof. 

 Zadock Thompson discovered fragments of trilobites in a portion of 

 the band, situated in the township of Highgate. Desiring to secure 

 all the light he could on the subject, he furnished several Palaeontolo- 

 gists with specimens of the fossils. These, however, failed to attract 

 much attention; in fact, they remained for the most part unnoticed; 

 thus the real age of the rock being still left, if not undetermined, at 

 least to a great extent unrecognized, it continued to be generally re- 

 garded as Medina Sandstone. 



This locality was often visited by Dr. G. M. Hall, of Swanton, and 

 myself, all along from 1855 to '60, and many specimens of the Sand- 

 stone, containing the remains of two or three species of fossils, were 

 from time to time collected by us. Early in the summer of 1861^ 

 E. Billings, Esq., of Montreal, while making explorations along the 

 Provincial line, called upon me. On my showing him several glabelliE 

 of the fossil trilobites, he at once remarked, they are Conocephalites, 

 and the rock must be Potsdam Sandstone. 



Waiving further reference to this matter, and without stopping to 

 mention the different individuals,* who have engaged with pains- 

 taking and praise-worthy zeal in the study of this formation, either at 

 an earlier or a more recent day, I may simply add, that since 1861 

 the rock has come to be very generally, if not universally, recognized 

 by geologists as belonging to the horizon of the Potsdam Sandstone. 

 And that this determination is correct, there can now, I think, be no 

 reasonable doubt. 



II. We may next ask, whether this Sandstone be succeeded, on 

 the east, by newer formations that have been disguised, as to their 

 age, by metamorphic action? 



* It gives me groat pleasure to refer in particular to the late Dr. E. Emmons, to the 

 late Professors C. B. Adams and Z. Thompson, to the late Trosident Hitchcoclc and 

 his associates in the geological survey of Vermont, to Sir William Logan and to 

 E. Billings, Esq., of the Canada survey, and last, but by no means least, to Pro- 

 fessor Jules Marcou, now of Paris, as gentlemen by whose labors I have been not a 

 little assisted, in various ways, in my study of the rocks of western Vermont. 



