THE DISTRIBUTION OF ANCIENT VOLCANIC ROCKS. 3 1 



to me for examination by Professor Eugene Smith of Alabama, 

 proved to contain nothing which could be identified as ancient 

 volcanic material. 



GENERAL CONCLUSIONS. 



The above rapid survey of the now known and probable areas 

 of ancient volcanic rocks in the crystalline portion of the Appa- 

 lachian system reveals the fact that this class of material is 

 both abundant and widely distributed. From Newfoundland to 

 Georgia it has been identified. For many areas the evidence of 

 surface or volcanic origin is conclusive, while in many others it 

 is as yet only probable. 



The areas of these ancient volcanic rocks now known fall 

 roughly in two parallel belts (see map); of these the eastern 

 embraces the exposures of Newfoundland, Cape Breton, Nova 

 Scotia, the Bay of Fundy, Coast of Maine, Boston basin and the 

 central Carolinas ; while the western belt crosses the Eastern 

 Townships and follows the Blue Ridge through southern Penn- 

 sylvania, Maryland, Virginia, North Carolina to Georgia. 



The purpose of the present communication will be accom- 

 plished if it succeeds in directing attention to this group of 

 rocks. New areas should be added ; probable areas investigated ; 

 and known areas monographed all along this old mountain range. 

 How fruitful a field is here spread out to students of geology 

 and petrography may be seen from the results of work in anal- 

 ogous regions by Harker^ and Miigge.3 



The identification of truly volcanic rocks in highly or partly 

 crystalline terrains possesses far more than a petrographical sig- 

 nificance, since by fixing what was the surface at the time of 

 their formation, they furnish a certain datum for tracing out the 

 sequence of later geographic changes and geological develop- 

 iTient. George Huntington Williams. 



' Am. Jour, of Science (3d ser.) Vol. 46, p. 47, July, 1893 ; and this Journal, Vol. i, 

 p. 179, 1893. 



^The Bala Volcanic Series of Caernarvonshire, Sedgwick prize essay for 1888, by 

 A. Harker, Cambridge, 1889. 



3 Untersuchungen iiber die " Lenneporphyre " in Westfalen und den angrenzenden 

 Gebietenby O. Mugge. Neues Jahrbuch fiir Min., etc., Beilage Band viii., pp. 525- 

 721, 1893. 



