454 ANNALS NEW YORK. ACADEMY OF SCIENCES 



The following program was then offered: 



A. W. Grabau, A Revised Classification of the North American 



SiLURic System. 

 Alexis A. Julien, On Determination of Mineral Constitution through 



Recasting of Analyses. 



Summary of Papers. 



Professor Grabau said in abstract: A review of the successive modifi- 

 cations of the classification of the Siluric system in North America brings 

 out the fact that the process of refining has been largely by separating 

 from this system divisions not properly belonging to it. Thus Dana in 

 1863 (first edition of the Manual) included the Cambric and Ordovicic 

 as "Lower Silurian," dividing it into Potsdam, Trenton and Hudson, and 

 dividing the "Upper Silurian" into Niagara, Salina and Lower Helderberg. 



In the 4th edition of the Manual (1895) the Cambric, Ordovicic and 

 Siluric Systems are recognized as distinct, though the name "Lower Silurian" 

 is still preferred for the Ordovicic. The three-fold division of the Siluric 

 is into: (1) Niagara, (2) Onondaga (SaHna) and (3) Lower Helderberg. 

 In 1899, Clarke and Schuchert published their revised classification of the 

 New York series, which has been pretty generally adopted. In this the 

 Helderbergian, exclusive of the Manlius, was separated as Lower Devonic, 

 while the remainder of the Siluric (Niagara and Onondaga (or Sahna) of 

 Dana, 1895) was divided into the Oswegan (Oneida conglomerate — Shaw- 

 angunk grit and Medina sandstone), the Niagaran (Clinton, Rochester, 

 Lockport and Guelph) and the Cayugan (Salina, Rondout and Manlius). 

 Since then Grabau and Hartnagel have independently demonstrated that 

 the Oneida is the equivalent of late Medina, and the Shawangunk, of Salina. 

 In 1905, Grabau suggested the Richmond age of the lower 1100 feet of the 

 Medina of western New York (Science XXII, p. 259, Oct. 27, 1905) uniting 

 the upper with the Clinton. These relations were more fully discussed in 

 1906 (Bull. 92, N. Y. State Museum) and again in 1907 before the Geolo- 

 gical Society of America, New York meeting, after a prolonged investigation 

 of the Appalachian deposits. This relationship is now fully established, 

 and the dividinff line between Ordovicic and Siluric is drawn at the base of 

 Upper TVledina or Medina proper. For the red INIedina shales, now recog- 

 nized as of Ordovicic age, the name Queenstown beds is proposed, from the 

 town of that name on the Niagara river opposite Lewiston, where these 

 beds are partly exposed. 



Recent studies by Grabau and Scherzer in southern jNIichigan and ad- 



