ElylSHA MITCHELL SCIENTIFIC SOCIETY. 25 



hardly be ready to put into systematic form for publi- 

 cation before the close of the year. A number of points 

 have been broug-ht out in the field-work, however, 

 that are considered to have sufficient bearing* on the 

 origin of the peridotites to warrant their presentation. 



THE ROCKS AND THEIR RELATIONS. 



The accompanying- map of the Appalachian cr3^stal- 

 line belt (Plate I) shows the distribution of the perid- 

 otites throug-hout this reg^ion. In Pennsylvania and 

 Maryland the basic mag^nesian rocks, whether orig-i- 

 nally peridotites or pyroxenites, have been entirely al- 

 tered into serpentine; and hence have lost most of their 

 orig-inal characteristics. The Virg'inia occurrences are 

 not so well known. Rog-ers' Reports show that many 

 of them have altered into serpentine and talcose rocks, 

 and this is doubtless true of the g-reat majorit}^ of out- 

 crops. Fresh olivine rocks, however, are found pass- 

 ing* over into that state from Alleg^hany county, North 

 Carolina, and they are doubtless to be found at a num- 

 ber of places on the belt, south of Lynchburg*. 



With few exceptions, the peridotites south of Vir- 

 g*inia are remarkably fresh, the alterations consisting*, 

 in the majority of cases, of scarcely more than surface 

 discoloration or an occasional local chang-e into massive 

 serpentine. 



The country rocks of the reg*ion are g-neisses and mi- 

 ca schists, sometimes bearing* considerable bodies of 

 sheared and massive g*ranites. The lamination has a 

 prevailing* strike of north 30° to 45*^ east and dips at 

 hig-h ang*les either northwest or southeast, often pass- 

 ing* throug*h the vertical from one to the other within 

 the space of a few feet. Constituting* a small propor- 

 tion of the area of this reg*ion are the rocks of the per- 



