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SCIENCE 



[N. S. Vol. XXIX. No. 746 



acter, in geological literature, as to the nature 

 and value of chemical criteria in distinguishing 

 schists of sedimentary from those of igneous 

 origin. Quantitative statements are wholly want- 

 ing. 



By compiling a large number of analyses of 

 pelitic sediments the writer showed the nature of 

 tue chemical changes involved in ttieir meta- 

 morphism. He then proceeded to contrast the 

 composition of the pelitic schists and gneisses 

 with that of their allies among igneous rocks. 

 The calculation of the " norm " of a schist and 

 its classification according to the quantitative 

 system of Cross, Iddings, Pirsson and Washington 

 was pointed out as a convenient method for 

 making such comparisons. 



These statistical studies brought out not only 

 the character of the chemical criteria which may 

 be used, but gave a quantitative measure of their 

 value. The paper concluded with the application 

 of these criteria to certain selected schist and 

 gneiss analyses. 



The discussion on this paper was participated 

 in by Professors B. K. Emerson, W. S. Bayley, 

 F. D. Adams and E. S. Bastin. 



After this the following paper was read by title: 

 Petrology of the South Carolina Oranites (Quartz 



Monzonites) : Thomas Leonabd Watson, Char- 

 lottesville, Va. 



The next two papers, being on related topics, 

 were presented in succession: 

 Tertiary Drainage Problems of Eastern North 



America: Amadeus W. Geabau, New York City. 



The Laurentian River of Spencer carried the 

 collected drainage of the Great Lakes through 

 Ontario Valley and out by the way of the present 

 St. Lawrence. The Finger Lake valleys and the 

 Genesee are regarded as made by tributary north- 

 ward flowing streams. Fairchild regards these as 

 northward-flowing tributaries of a (possibly) 

 westward-flowing river in the Ontario Valley. 

 The author has in the past shown that a normal 

 sequential drainage system, the general direction 

 of which was northward, and in which the minor 

 streams were beheaded by the master, accounted 

 for all the topographic features of the region in 

 question. Subsequent blocking of some of the 

 channels by drift and deepening of others by ice, 

 and a general depression of the country to the 

 northeast, has produced the present drainage sys- 

 tem. The problems were discussed in the light of 

 accumulated facts. 

 Drainage Evolution in Central New York: H. L. 



Faiechild, Rochester, N. Y. 



The paper aimed to assist in the elucidation of 

 the complete physiography of the west half of 

 New York State. Three maps represented graph- 

 ically the general evolution of the drainage and 

 the interference by glacier invasion of the normal 

 stream development. 



The first map showed the existing valleys which 

 are an inheritance from the primitive (conse- 

 quent) drainage, southwestward, across the uplift- 

 ing coastal plain. These inherited valleys fall 

 into three classes: (a) those in which the present 

 flow is the same as the primitive, (6) those which 

 are abandoned or left as " hanging " valleys and 

 (c) those in which the stream flow has been re- 

 versed. A remarkable parallelism is exhibited by 

 these valleys, which, except in the district of the 

 Delaware and upper Susquehanna, are transverse 

 to the present master streams. The primitive 

 Susquehanna continued directly south at Lanes- 

 boro, instead of bending northwest as now, and 

 occupied in Pennsylvania the Tunkannock Valley. 

 Other valleys in northern Pennsylvania represent 

 the continuation of the southwestward flow in 

 central New York. 



The second map exhibited the hypothetical Ter- 

 tiary drainage. During Mesozoic and Tertiary 

 time all the drainage of the west half of the state 

 was diverted westward (subsequent) and north- 

 ward (obsequent) into a great trunk stream that 

 occupied the Ontario and Erie valleys and prob- 

 ably drained westward into the Mississippi basin. 

 The cause of this radical reversion of flow was 

 the great thickness of non-resistant rocks in the 

 Ontario district. In the vertical series of strata 

 between the Trenton and the Portage, on the Cay- 

 uga meridian, are 5,150 feet of rock of which 

 4,500 feet are weak shales, 350 feet limestone and 

 250 feet sandstone. 



The pre-Glacial divide was far south in Penn- 

 sylvania. The Allegheny system poured north 

 through the lower Cattaraugus Valley. The upper 

 Genesee was tributary to the broad Dansville- 

 Avon River, which almost certainly had its north- 

 ward course through the Irondequoit Valley. The 

 Susquehanna turned west from the site of Lanes- 

 boro and Susquehanna villages along the strike of 

 the Chemung strata, which were less resistant 

 than the overlying Catskill, past the sites of Bing- 

 hamton, Owego and Waverly, and then curved 

 north through the sites of Elmira and Horseheads 

 and occupied the Seneca Valley. The Chemung 

 was the principal tributary from the west, as 

 to-day, but it passed north of Elmira instead of 

 south, where it now lies in a post-Glacial cut. 



The Delaware and the upper tributaries of the 



