750 



SCIENCE 



[N. S. Vol. XXIX. No. 749 



hour was allowed for the presentation and dis- 

 cussion of each topic; the principal speaker took 

 thirty minutes or less; the remainder of the 

 time was given to discussion of the subject as 

 presented by him. The following speaker was 

 not allowed to begin until the hour stated on the 

 program had arrived. This plan appeared to 

 work to the satisfaction of the audience; the 

 speakers confined themselves practically to the 

 time allotted, and their convenience and that of 

 all who had an interest in the subject was satis- 

 factorily served. 



The papers contributed to the symposiiun will 

 appear in the Journal of Geology of Chicago Uni- 

 versity, in chronological order. 



Monday morning at 11 A.M. in a subsection, 

 with G. K. Gilbert as chairman, the following 

 papers were read: 

 Some JVew or Little-known Geological Terms and 



their Application in Stratigraphic Writing: 



A. W. Gbabau. 



The following terms were discussed and defined : 



1. Disconformity, proposed by Grabau in 1905 

 to cover unconformable relation of strata where 

 no discordance of dip exists, the term uncon- 

 formity being restricted to cases with perceptible 

 discordance of dip. 



2. Rudaceous and rudyte, arenaceous and ar- 

 enyte, lutaceous and lutyte, proposed by Grabau 

 in 1904 for pebbly, sand and mud rocks, respect- 

 ively, irrespective of their composition; classifica- 

 tion of clastic rocks by texture being advocated. 

 According to composition we may have: silici- 

 rudytes, silicarenytes, silioilutytes ; calcirudytes, 

 calcarenytes, oalcilutytes ; argillutytes, etc. 



3. Ghronofauna and chronoflora and locofauna 

 and locoflora (new), the first two for fauna and 

 flora of a given time period, the other two for the 

 fauna and flora of a locality. 



4. Epiplankton (new) for organisms attached 

 to floating objects and not primarily planktonic. 

 There have been included under this term pseudo- 

 plankton, which it is proposed to restrict to dead 

 organic and to inorganic planktonic matter. 



5. Epicontinental sea to be restricted to the 

 shallow seas lying within the continents and con- 

 stituting with the mediterraneans the intracon- 

 tinental seas. The term littoral to be applied as 

 in zoology to the district extending from high 

 water to limit of sun-illuminated bottom (edge 

 of continental shelf in the oceans) and character- 

 istic of oceans, intracontinental seas and lakes. 

 The term epicontinental sea is not to be applied 

 to the littoral district of the oceans as thus de- 

 fined. 



Hon to be active — in search of food, 

 escape from enemies, etc.; dispersal to be passive 

 — by currents, water or air, etc., or by carriage 

 by other organisms, etc. 



This paper was discussed by G. K. Gilbert. 



Some Preglacial Valleys in Eastern New York 



and Their Relation to Emisting Drainage: John 



H. Cook. 



The valley of the Mohawk from Schenectady to 

 the Hudson River is of post-glacial origin, as 

 shown by the fact that between Niskayuna and 

 Fort's Ferry it crosses a filled channel, trending 

 north-northeast towards Round Lake and south 

 towards Albany (at which city this channel prob- 

 ably opens into the Hudson valley) . 



For two miles above Schenectady borings along 

 the Mohawk developed no rock at a depth consid- 

 erably below the rock bottom of the river at the 

 entrance to the upper gorge near Rexford Flats. 



The channel of the preglacial Mohawk lies be- 

 neath the sediments of glacial Lake Albany, but 

 may be traced approximately. It parallels, 

 roughly, the Helderberg escarpment and probably 

 reaches the Hudson just north of Coeyman, where 

 there is a break in the rock wall elsewhere almost 

 continuously exposed for several miles north and 

 south of that point. 



Drift and sands and clays deposited during the 

 retreat of the ice sheet had filled these channels 

 and spread widely over the divides when the re- 

 excavation of the Hudson valley and the draining 

 of Lake Albany were accomplished. The waters 

 of Lake Iroquois still found outlet through the 

 Mohawk valley as far as Schenectady, but, as a 

 point near Rexford Flats lay at an elevation below 

 the level of the deposits immediately south and 

 west, the stream there poured over the low divide, 

 crossed the filled channel mentioned above and 

 took the course it now pursues to the Hudson. 



This paper was discussed by G. K. Gilbert and 

 F. P. Gulliver. 



Monday afternoon, following the vice-presiden- 

 tial address of J. P. Iddings on "The Study of 

 Igneous Rocks," the reading of papers was con- 

 tinued. 



The Metamorphism of Glacial Deposits: Fbank 

 Carney. 



Till and tillite are two extremes in the structure 

 of glacial deposits. 



So far as we yet know, the periods of glaciation 

 are spaced by long lapses of time; therefore we 

 have only disconnected data in the metamorphio 

 cycle of glacial sediments. 



