RECORDS. 315 



Summary of Papers. 



Dr. Julien stated that the term ''inclusive" is commonly 

 applied, by the petrograper, to ordinary dikes of igneous rock, 

 surrounded by beds of sedimentary rock or of crystalline 

 schists, intersecting them or intervening between their foliation 

 planes. But for similar masses cut loose from all connection 

 with the underlying magmatic source, swallowed up within strata 

 of crystalline schists, and experiencing all stages in the process 

 of reaction and final absorption, during metamorphic change, 

 another term seems to be called for, viz., " occlusion," signi- 

 fying shut or sealed up beyond escape. Although the word is 

 borrowed from the physicist, this can produce no confusion when 

 applied to petrographic phenomena. Occluded igneous rocks 

 may belong to either the acid or basic class, as illustrated re- 

 spectively, on Manhattan Island, by the earlier intrusions of 

 pegmatite, never found as intersecting dikes, and by the inter- 

 calated sheets of dionite-schist. Occlusion is usually attended 

 by mechanical and chemical processes. The former consists of 

 thinning or thickening of igneous masses caught between the 

 folia of schists, during orogenic movements, into lenticular 

 masses ; the crumpling and corrugation of sheets, and even 

 rolling into cylinders ; and the forcing of the pasty masses 

 along foliation planes, in the form of intercalated or " secondary " 

 dikes. The chemical processes usually consist of micaceous 

 alteration and ultimate absorption by disintegration and dissem- 

 ination through the surrounding country rock. 



In discussing this paper. Professor Kemp spoke of the value 

 of the interpretation to those who have studied the region. 



Dr. Matthew presented a series of w^orld-maps showing the 

 hypothetical outlines of the continents during the Pleistocene, 

 Pliocene, Miocene, Oligocene, later Eocene, and at the opening 

 of the Tertiary period, as contrasted with the modern conditions. 

 The series was got up for use in the Hall of Fossil Mammals, in 

 the American Museum of Natural History, to illustrate the geo- 

 graphical distribution of different groups of mammals during 

 the successive epochs of the Tertiary and Quaternary. It is 

 intended to represent a somewhat conservative view of past 



