224 



SCIENCE. 



[N. S. Vol. XXI. Xo. 528. 



has the concluding chapter on the ' Tectonic 

 Geograpliy of Eastern Asia.' G. P. Grinisle.y 

 contributes a paper entitled ' A Theory cf 

 Origin for the Michigan G3T)sum Deposits,' 

 in which he supposes that they were deposited 

 in an interior sea, and in explanation of the 

 localization of the deposits compares it with 

 the present Caspian Sea. 



SOCIETIES AND ACADEMIES. 



THE GEOLOGICAL SOCIETY OF WASHINGTON. 



The 161st meeting of the society was held 

 on Wednesday evening, January 11, 1905. 

 The regular program comprised the following 

 communications : 



Undulations of Certain Layers of the Lock- 

 port Limestone: Mr. G. K. Gilbert. 

 Mr. Gilbert exhibited photographic views of 

 two structures affecting beds near the top of 

 the Lockport limestone. These had been pre- 

 viously described and figured by Hall, in his 

 report on the geology of the fourth district of 

 New York. One structure is a system of 

 domes or arches occupying the whole surface 

 of the rock and separated by narrow synclines. 

 They are usually several feet in diameter, and 

 are repeated downward through a series of 

 strata. The other structure is a manmiilla- 

 tion somewhat resembling ripple marks, and 

 with a diameter of about one inch. The two 

 structures occur in the same strata. The 

 photographs were made in a new railroad cut- 

 ting within the city of Niagara Falls, in a 

 <iuarry three miles east of the city, and in 

 water channels temporarily exposed at the 

 Dufferin Islands, on the Canadian side. Mr. 

 Gilbert was not satisfied with Hall's charac- 

 terization of the structures as concretionary, 

 but suggested no alternative. He thought 

 them contemporary with the deposition of the 

 strata, and not subsequent. 



The Great Fault of the Bitterroot Mountains: 



Mr. W. LiNIKJREN. 



The Bitterroot Mountains in the western 

 part of Montana rise for a distance of eighty 

 miles like a long narrow block above the gen- 

 eral level of a greatly dissected plateau or 

 peneplain which extends over a large area in 

 central Idaho and a part of the adjacent state 



of ]Montana. On the east the Bitterroot 

 Mountains descend from an elevation of 9,000 

 feet to the level of the wide Bitterroot valley. 

 From one end of the range to the other this 

 slope is remarkably even and gentle, having 

 an average declivity of twenty degrees. Its 

 face consists of a zone of granite schist, per- 

 haps averaging 1,000 feet thick, in which 

 pressing and deformation of the crystals are 

 intimately associated with numberless slipping 

 planes with striation parallel to the slope of 

 the front plane. The predominant rock of 

 the range is a quartz monzonite with transi- 

 tions into granite. These facts are inter- 

 preted as meaning that the frontal slope is 

 formed by a great flat fault of normal char- 

 acter, along which both molecular and molar 

 movement has occurred. The horizontal com- 

 ponent would be at least 15,000 feet, the ver- 

 tical at least 4,000. The depth below the sur- 

 face at which this zone of schistosity was 

 foi-med can scarcely have been more than 2.000 

 to 4,000 feet. The age of the uplifted pene- 

 plain is believed to be late Mesozoic and the 

 fault is probably but little later. Slight 

 faulting movements seem to continue along 

 it up to the present time. 



Artesian Water in Crystalline Rocks: Mr. 

 Geo. Otis Smith. 



The presence of artesian water in an area 

 of crystalline rocks in the vicinity of York, 

 Me., presents a hydrologic problem little dis- 

 cussed in geological literature. With closely 

 folded and thoroughly indurated rocks the 

 water circulation in the deeper rock zone must 

 be along schistosity partings and joint open- 

 ings rather than through pore openings in a 

 gently inclined porous stratum. The im- 

 pervious cover essential to the artesian type 

 of supply of ground water is furnished by 

 the greater degree of cementation of the nat- 

 ural openings in the rock near the surface. 

 It thus follows that the pressure under Mhich 

 the water circulates in the rock becomes in- 

 sufficient to overcome the internal friction 

 near the surface, and upward escape is pre- 

 vented. When a free vertical channel is 

 provided by a well, the water rises in the well 

 and in three cases cited overflows at the sur- 

 face. The results of this hydrologic investi- 



