524 



SCIENCE. 



[N.S. Vol. XIX. No. 483. 



of remarkable forms, produced by erosion, 

 known as tbe 'City of Rocks.' 



New Studies in the Ammonoosac District 

 of New Eampshire: C. H. Hitchcock. 

 For several years the author has been in- 

 vestigating the geology of the only part of 

 New Hampshire which yields fossils, hoping 

 to be able to interpret the mutual relations 

 of the several formations as revealed by 

 paleontology and a better understanding of 

 the petrogr,aphy. The fossils have been 

 renamed by Mr. Schuchert. (1) The rock 

 masses in this district formerly referred 

 to; porphyritie gneiss, lake gneiss, Bethle- 

 hem gneiss, protogene, diorite and horn- 

 blendites are now regarded as igneous in- 

 stead of metamorphic stratified terranes. 

 (2) The fossils belong to the middle upper 

 Silurian. (3) The rocks of Blueberry 

 Mountain exhibit the synclinal structure- 

 consisting in the upward order of lime- 

 stones, argillite, conglomerate and black 

 argillites. Only the limestones contain 

 fossils. (4) Different ranges of argillite 

 having somewhat diverse petrographical 

 character are now esteemed to be equivalent 

 —the variations being supposed to have 

 been occasioned by a greater or less meta- 

 morphic action. (5) Careful scrutiny of 

 the slates reveals both a cleavage different 

 from the stratification, and a structure 

 analogous to stratification produced by a 

 multitude of minute fractures. (6) The 

 areal distribution and stratigraphy of the 

 'auriferous conglomerate' suggests its iden- 

 tity with the 'Coos quartzite' — a forma- 

 tion traceable southerly into Massachusetts 

 down the Connecticut valley. (7) The 

 numerous fractures in this conglomerate 

 indicate that the whole region is but a 

 mosaic of faulted fragments. (8) This 

 better understanding of the Ammonoosac 

 rocks can not fail to improve our interpre- 

 tations of the ages of the adjacent crystal- 

 line groups in northern New England. 



Studies in the Western Finger Lake Re- 

 gion: Charles R. Deter. (Illustrated 

 with lantern slides.) 



The region discussed lies in western New 

 York, between Canandaigua Lake and the- 

 Genesee River. The northward slope of 

 the Allegheny plateau is here trenched by 

 deep, narrow valleys, four of which con- 

 tain small lakes, while a fifth is lakeless. 

 These valleys are similar in general char- 

 acter to those of the larger Finger lakes, 

 but bear peculiar relations to one another- 

 and to the east-west Cohocton valley. In 

 several cases the head of a minor valley 

 opens broadly into the side of a major 

 valley but a few hundred feet above its 

 floor, thus sustaining the relations of a 

 headward hanging valley. These are 

 thought to furnish criteria for estimating- 

 the amount of differential deepening by 

 ice erosion. The main valley heads ai"e 

 blocked by massive terminal moraines and 

 overwash plains. The steep valley slopes: 

 are broken by rock terraces which support 

 well-developed marginal moraines. Pitted 

 or morainal deltas indicate the existence of 

 high-level marginal lakes. Transverse 

 passes and high-level longitudinal valleys 

 are choked for many miles with morainal 

 ■^deposits terminating in an overwash plain. 

 Some of the principal ridges present driun- 

 linoid profile, while their lateral slopes were 

 greatly oversteepened. The phenomena 

 indicate that during the late "Wisconsin 

 period the region was occupied by a com- 

 plex system of distributary and intercept- 

 ing ice streams, to which the present depths 

 and sharpness of the valleys are chiefly due.. 



Note on the Geology of the Hellgate Valley 

 between Missoula and Elliston, and 

 Northward to Placid Lake, in Montana r 

 N. H. WiNCHELL. (Read by title.) 

 This paper gives an account of the gen- 

 eral stratigraphy extending from the oldest 

 sediments (Algonkian) to the Cretaceous 



