194 Geological Society : — 



the ancient St. Lawrence (Laurentian) river, with a great tributary 

 from the Erie basin and another across the southern part of the State 

 of Michigan. This valley is of high antiquity, and was formed during 

 times of high continental elevation, culminating not long before the 

 Pleistocene period. The glaciation of the region is nowhere parallel 

 with the escarpments, forming the sides of, or crossing the lakes or 

 less prominent features. During the Pleistocene period, and especially 

 at the close of the episode of the upper Till, the continent was greatly 

 depressed, and extensive beaches and shore-lines were made, which 

 are now preserved at high elevations. With the re-elevation of the 

 continent these old water-levels have been deformed, owing to their 

 unequal elevations. This deformation is sufficient to account for the 

 rocky barriers at the outlets of the lakes. Some of the lakes have 

 been formed, in part, by drift obstructing the old valley. The 

 origin of the basins of the Great Lakes may be stated as the 

 valley (of erosion) of the ancient St. Lawrence Eiver and its 

 tributaries, obstructed during, and particularly at the close of, the 

 Pleistocene period, by terrestrial movements, warping the earth's 

 crust into barriers, thus producing lake-basins, some of which had 

 just been formed in part by drift deposited in the ancient valley. 



3. " On Ornithosaurian Remains from the Oxford Clay of North- 

 ampton." By R. Lydekker, Esq., B.A., F.G.S. 



4. " Notes on a ' Wash-out' found in the Pleasley and Teversall 

 Collieries, Derbyshire and Nottinghamshire." By J. C. B. Hendy,Esq. 



Sections were given of the " Wash " showing the thickening of the 

 coal as it approaches the same, and the splitting of the " Wash " 

 itself into two branches. Various measurements were noted, and 

 certain disturbances recorded. In every section examined, the sides 

 of the " Wash " are more or less slickensided, and in some few cases 

 the coal is distorted next to the " Wash; " but the author is of opinion 

 that these are due to lateral pressure and movement subsequent to 

 the denudation of the coal and deposition of the sandstone, and he 

 remarks on the difficulty of reconciling the regularity of the under- 

 clay with the theory of the formation of " Washes " by disturbance. 



He considers that they are due, in Durham and elsewhere, to 

 currents flowing at a high rate of speed in one direction, carrying 

 away the denuded material, and, as in the case of the Derbyshire 

 " Wash," to a series of inundations, each inrush denuding a certain 

 amount, and on subsiding redepositing part of the material at a 

 higher level, while the remainder was carried away in suspension. 



In conclusion, notice was taken of " washes " occurring in other 

 localities. 



April 30. — Dr. A. Geikie, E.R.S., President, in the Chair. 



The following communications were read : — 



1. "On certain Physical Peculiarities exhibited by the so-called 

 * Raised Beaches ' of Hope's Nose and the Thatcher Rock, Devon." 

 By D. Pidgeon, Esq., F.G.S. 



The author described the peculiarities of these so-called beaches, 



