RECORDS 507 



This conclusion removes many of the gneisses from the group 

 of uncertainties. 



The speaker also briefly enumerated the discoveiy of new 

 outliers of Cambrian and Ordovician strata in the midst of the 

 crystallines ; taking up the small but early discovered area at 

 Wellstown, Hamilton county, he added some new and important 

 facts and interpretations. He also noted the distribution of the 

 glacial striations throughout the eastern mountains and noted 

 their nearly uniform bearing to the northeast. In conclusion, 

 he described the physiography as being due chiefly to a series 

 of faulted blocks which afford a very characteristic saw-toothed 

 sky-line. 



Dr. Julien opened his paper with a discussion of several of 

 the later theories of the origin of pegmatites in common accepta- 

 tion. That of igneous intrusion, urged by Brogger, seems to 

 cover facts which are not met with in the pegmatites of Manhat- 

 tan Island, western Massachusetts nor western North Carolina. 

 Brogger' s theory and the pneumatolytic theory of Lehmann, 

 Williams and Crosby, explain but imperfectly the most import- 

 ant occurrences of pegmatite occurrences in schists, especially 

 evidences of their development in loco. Dr. Julien then sum- 

 marized his own theory of metasomatic aggregation which he 

 originally advanced at the meeting of the American Association 

 for the Advancement of Science in June, 1900. In this he at- 

 tributed the origin of the pegmatites of Manhattan Island entirely 

 to molecular rearrangement of the material of the schists by the 

 action of mineralizers in the vicinity of lamination planes and of 

 fissures'. 



After a description of the main features of the pegmatites of 

 Manhattan Island, with the help of specimens and diagrammatic 

 drawings of outcrops and cross-sections, the speaker advanced 

 the following chief conclusions : 



I . The existence of a certain series of pegmatite development, 

 at least two, but probably indefinite in number, marked by a 

 succession of intersections. Of these the oldest is by far the 

 most extensive, intercalated among the pliation-seams, and co- 

 incident with the strike. These pliation-seams cut the schists in 



