924 



SCIENCE. 



[N. S. Vol. XII. No. 311. 



points to the conclusion that this formation, of 

 a thickness of at least a thousand feet, was 

 formed as a flood plain deposit. Its charac- 

 teristics, except color, are the same as the New 

 Jersey and Connecticut valley Jurassic sand- 

 stones. Ripple-marks, sun-cracks, cross-bed- 

 ding, channel -fillings, etc., are abundant. In 

 the railroad cut west of Otisville the grit lies 

 upon Hudson shales, with non-coincident dip. 

 On the contact occurs a few inches of clay, 

 which next to the shale, is quite free of pebbles, 

 while next the grit it is filled with quartz peb- 

 bles. This was interpreted to be residual clay 

 caused by the decomposition of the shale, 

 through sub-aerial agencies, before it became 

 covered by the grit. The old notions regai'ding 

 rock-formation required the presence of a body 

 of water in which the sediments might be de- 

 posited. Several of the geological subdivisions 

 showed characters which would not have been 

 present had these formations been laid down 

 under water, for this mode of origin results in 

 a sorting of the rock-forming materials, and no 

 sorting is detected in these grits. Flood plain 

 deposits are very irregular, both as to stratifi- 

 cation and sorting of materials, and these fea- 

 tures are well exhibited in the grits. Other 

 formations that are probably plain-flood deposits 

 are parts of the Potsdam sandstone in eastern 

 New York, the Medina sandstone, the sand- 

 stones of the Catskill group, and many of the 

 sandstones of the coal measures of Pennsylvania 

 and the Mississippi valley — in fact the greater 

 part of the ' Barren Measures.' 



Dr. Theodore G. White presented notes on 

 'The Glen Falls, N. Y., section of the Lower 

 Ordovician,' described his detailed study of the 

 faunas of successive strata at Glen Falls, and 

 their relations to similar studies along the Lake 

 Champlain valley to the north, and the Mohawk 

 and the Black Eiver valleys to the west. The 

 section forms a low anticline along the shore of 

 the Hudson. At the base is seen the Calcifei-ous 

 sandrock, containing Ophileta and fucoids. Con- 

 formable upon this is a layer a few inches thick, 

 of barren black shale, which is very much 

 crushed, and then the same beds of the ostra- 

 cod, Leperditia, and their associated corals and 

 peculiar forms of Strophomena, as have been 

 found in the lowest Black River zones on 



Button Island in Lake Champlain. The zones 

 of Parastrophia and Tripleaia, occurring near 

 this portion of the series in localities to the 

 north and west, were not found here. The 

 succeeding coral beds of Columnaria were well 

 developed. Above these are the cross bedded 

 gray beds, which in some recent reports have 

 been considered to represent the Birdseye lime- 

 stone, which seems to be lacking in this locality, 

 unless met with at this unexpectedly high posi- 

 tion. The upper portion of the section, which 

 is of lower Trenton age, shows no unusual 

 forms. The tendency of the lowest and the 

 uppermost portions of the Ordovician sections 

 in the region to wear away and appear wanting, 

 owing to their prevailing softness, was com- 

 mented on. 



Dr. Henry S. Washington read a paper on 

 'The Rocks of Lake Winnipesaukee, N. H.,' 

 as a preliminary report on work done by Pro- 

 fessor Pirsson and himself on Mount Belknap 

 and Red Hill, near Lake Winnepesaukee, 

 N. H. The rocks of Mount Belknap are shown 

 to be prominently a quite uniform alkali 

 syenite, which is cut by many dikes of camp- 

 tonite and allied rocks, and of bostonites, 

 aplites and sj'enite-porphyries. These dikes 

 also cut the surrounding porphyritic gneiss. 

 At one place, near the border, is a mass of 

 basic hornblende-gabbro, with large, poikilitic 

 phenocrysts of brown hornblende. A syenite 

 breccia also occurs. At Red Hill similar syenite, 

 formerly described by W. S. Bayley, occurs 

 on the summit, while, toward the periphery, 

 nephaline appears as a constituent, and a true 

 foyaite is developed. The massif is also cut by 

 dikes, both camptonitic and syenitic. The 

 region is to form the subject of a petrographic 

 study by the two geologists in the near future. 



Professor Daniel S. Martin described a visit 

 which he paid during the summer to the noted 

 mineral locality at Haddam, Maine. He de- 

 scribed the manner in which the choicest speci- 

 mens occur there, in veins of albitic pegama- 

 tite, with tourmaline, muscovite and quartz 

 along the contact with the wall of gneiss. The 

 mica plates along the contact are often two feet 

 in diameter. 



Dr. A. A. Julien in his paper ' The Geology 

 of Central Cape Cod ' reviewed the opinions of 



