400 



SCIENCE. 



[N. S. Vol. II. No. 39. 



by shearing and is therefore parallel to the 

 bedding, and this maj' be called parallel 

 cleavage or parallel fissility. In heteroge- 

 neous rocks, however, at the crests and 

 troughs the law of hydrostatic flow chieflj'' 

 applies, while the law of shearing applies 

 at the limbs. In passing from the limbs 

 of the folds to the arches and troughs the 

 two tendencies are both at work, and the 

 phenomena are the resultants of both forces. 

 The law of hydrostatic viscous flow becomes 

 predominant as the arch or trough is 

 neared ; the law of shearing, as the limb is 

 approached. 



Professor B. K. Emerson, Amherst, Mass., 

 delivered the substance of two papers on 

 the Archtean and Cambrian rocks of the 

 Green Mountain range in southern Mass- 

 achusetts and on the geology of Worcester 

 County, Mass., which embodied a prelimi- 

 narjf account of the author's work on the 

 region for the United States Geological Sur- 

 vey. The Green Mountains traverse west- 

 ern Massachusetts in a series of complex 

 anticlines and synclines which are partly 

 overturned and over thrust westward . Upon 

 these in places there is unconformable con- 

 glomerate gneiss of Cambrian age. The 

 author illustrated bj'' means of the United 

 States Geological Survej- topographic maps 

 the progress of the work in mapping the in- 

 tricate crystalline rocks in the district. 



' Gotham's Cave, or Fractured Eocks in 

 ISTorthern Vermont ' was the title of a short 

 paper by Professor C. H. Hitchcock, N. H., 

 describing with the aid of sketch maps and 

 sections a peculiar occurrence in the Green 

 Mountain State. 



' Recent discovery of the occurrence of 

 marine cretaceous strata on Long Island.' 

 In this paper Mr. Arthur Hollick, of Co- 

 lumbia College, said that the presence on 

 Long Island of cretaceous strata belonging 

 to the so-called non-marine division was 

 amply demonstrated some years ago, but 

 until the past year the evidence of the ex- 



istence there of marine strata of this age 

 was confined almost entirely to the alleged 

 discovery of an Exogyra in an excavation 

 for a well in Brooklyn. Last summer, 

 while examining the north shore at Center 

 Island, evidences of more strata were ob- 

 served, and afterwards hardened fragments 

 of marl containing Ch-yj)hcea and other cre- 

 taceous molluscs were found in the moraine 

 near Ridge wood Reservoir, Brooklyn. 



Dr. J. AV. Spencer read a contribution 

 on the ' Geological Canals between the 

 Atlantic and Pacific Oceans.' He said that 

 over the Isthmus of Tehuantepec, in Mexico, 

 low planes now eroded mark a shallow 

 strait of a few miles in width connecting 

 the basin of the Mexican Gulf with that of 

 the Pacific Ocean. This land is now raised 

 about 1,000 feet above sea level. Through 

 these straits there are two lower canals 

 about 800 feet above tide, only a mile long 

 and a quarter of a mile wide, whose floors 

 are covered with gravels which are con- 

 tinuous with terraces upon the gulf side. 

 The time of elevation is that of the recent 

 terrace epoch; at any rate it was later than 

 the Columbia period. 



A second paper by Dr. Spencer dealt 

 with the 'Recent Elevation of New England.' 

 He holds that the high terraces in the val- 

 leys of New England are not those of rivers 

 but of estuaries. These terraces occur on 

 the north, east, south and west sides of the 

 New England rivers from an elevation of 

 at least 2,700 feet downward by level steps. 

 From their features it is inferred that these 

 steps represent changes in the base plane 

 of erosion, or, in other words, successive up- 

 lifts in the most recent post-glacial times in 

 amount aj)proximately equal to the aggre- 

 gate heights of tlie terraces. The elevation 

 appears to have been greater in the moun- 

 tain masses than "nearer the sea. 



' Geological Notes on the Isles of Shoals,' 

 by Dr. H. C. Hovey, Newburyport, Mass. 

 The author briefly described these islands, 



