416 



SCIENCE 



[N. S. Vol. XXX. No. 769 



erosion is possible under certain conditions, the 

 occurrence of hanging valleys of this type is 

 exceptional, and their peculiar origin may be 

 detected by associated physiographic features. It 

 was concluded that in general hanging tributary 

 valleys of the common type are to be regarded 

 as proof of glacial erosion. A study of the rela- 

 tions normally existing between stream valleys 

 and their tributaries proves that hanging tribu- 

 tary valleys of any length can hardly be produced 

 by glacial widening of the main valley, and that 

 where such hanging valleys exist a significant 

 amount of glacial over-deepening must be inferred. 

 A method of estimating the actual amount of 

 glacial over-deepening of valleys with a fair de- 

 gree of accuracy was described, and the applica- 

 tion of this method to glaciated valleys in Europe 

 was discussed. Glacial over-deepening amounting 

 from 600 to over 1,000 feet was found to have 

 occurred in three of the valleys studied. 



On the basis of this study it was concluded that 

 no account of drainage modifications in glaciated 

 regions could be regarded as complete if it failed 

 to take account of the possible changes due to 

 glacial erosion. The relation of this study to the 

 drainage problems in western New York, and to 

 engineering problems in the gorge of the Hudson 

 River, was briefly touched upon. 

 The Early Paleozoic of the Lehigh Valley District, 

 Pennsylvania: Edgae T. Wheeby, Lehigh Uni- 

 versity. 



Contrary to the usual opinion, it has been found 

 that the Cambrian and Ordovician portions of the 

 Great Valley limestones in this district can be 

 readily distinguished on a lithologic basis, five 

 formations being recognizable between the Hardy- 

 ston quartzite of Lower Cambrian age and the 

 Martinsburg shale of Lower Trenton to Utica age, 

 as follows {local names being provisionally ap- 

 plied, and the thicknesses roughly estimated) : 

 Leithsville formation, Lower-Middle Cambrian, 

 gray dolomite with abundant sandy and cherty 

 layers, and buff-colored shale beds, 1,500 feet. 

 AUentown limestone. Upper Cambrian, white to 

 gray, dolomitic, largely oolitic, full of Crypto- 

 zoon, 2,000 feet. Coplay limestone, Beekmantown, 

 dark gray, shaly, with mottled crystalline layers, 

 numerous fossils, 1,500 feet. A marked erosion 

 interval occurs here, so that the whole thickness 

 of the Coplay is rarely seen. Nisky formation, 

 Black River, gray, very shaly limestone, probably 

 never exceeding 100 feet in thickness. Nazareth 

 cement rock, Lower Trenton, varying from 500 



feet or more down to zero, being replaced west- 

 ward and southward by the Martinsburg shale. 

 The presence of two small areas of Shawangunk 

 conglomerate, preserved by down-faulting some 

 twenty miles south of the main exposure in the 

 Blue Ridge, corresponding in position and lith- 

 ologic character to the Green Pond of New Jersey, 

 is also announced. 



Characteristics of the Older Crystallines of South- 

 eastern New York: Chables P. Bbekey, Colum- 

 bia University. 



There are but three well-established formations 

 belonging to the completely metamorphosed series 

 of the vicinity of New York City. These are: 



(a) Fordham gneiss and its associates (oldest). 



(6) Inwood limestone. 



(o) Manhattan schist (youngest). 



The Fordham gneiss and Manhattan schist are 

 not always readily distinguished. Certain varie- 

 ties of each are alike in every essential character, 

 and if the evidence is confined to these varieties 

 no determination can be made. This is especially 

 true of the intrusive members. 



A study of thousands of cases where discrim- 

 ination between these two formations was neces- 

 sary has convinced the writer that the most con- 

 stant characters of the Manhattan schist in order 

 of importance are: 



(a) The presence of a white pearly mica. 



(6) Coarse foliation. 



(c) A crumpled structure. 



And in contrast the most constant Fordham 

 gneiss characters are: 



(a) A banded structure. 



( 6 ) Close granular or granitoid texture merging 

 into foliation. 



(c) Abundance of feldspathic constituents. 



During the past year a study of Manhattan 

 Island, especially the covered portion of the 

 southern third, and adjacent areas southward on 

 Long Island, has been made by means of an exam- 

 ination of all drill borings whose materials could 

 be seen — several hundred in all. Discrimination 

 by the above criteria indicates a much more com- 

 plex structure and areal distribution than for- 

 merly mapped. Both gneiss and limestone are 

 represented in these southerly areas. Recent bor- 

 ings placed for the purpose of testing this struc- 

 ture have proved the case beyond any question by 

 penetrating both of these formations at points 

 indicated by this interpretation. 



Edgae T. Whebet, 



Secretary 



