XXXVII. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 

 [Continued from p. 175.] 



November 5th. 1902.— Prof. Charles Lapworth, LL.D., F.R.S., 

 President, in the Chair. 



r |\HE following communications were read: — 

 -*■ 1. ' The Fossil Flora of the Cumberland Coalfield, and the Palseo- 

 botanical Evidence with regard to the Age of the Beds.' By E. A. 

 Newell Arber, Esq., M.A., F.G.S. 



2. ; Some Remarks upon Mr. E. A. Newell Arber's Commu- 

 nication : On the Clarke Collection of Fossil Plants from New 

 South Wales/ By Dr. F. Kurtz, Professor of Botany in the 

 University of Cordoba, Argentine Republic. 



3. ' On a new Boring at Caythorpe (Lincolnshire).' By Henrv 

 Preston, Esq., F.G.S. 



This boring, after piercing Northampton Sands, passed through 

 199 feet of Upper Lias, 19 feet of Marlstone, and into the Middle 

 Liassic Clays. With the aid of other shallow wells in the Lincoln- 

 shire Limestone, the author shows that this rock has a decided dip 

 to the west down the face of the escarpment, as though it had 

 settled down upon the eroded surface of the Upper Liassic Clay. 

 This settlement is probably the cause of a continuous spring flowing 

 from the junction, and it has given rise to an underestimate of the 

 thickness of the L'pper Lias. 



Xovember 19th. — Prof. Charles Lapworth, LL.D., F.R.S., 



President, in the Chair. 



The following communications were read : — 



1. ' The Semna Cataract or Rapid of the Nile : a Study in 

 River-Erosion.' By John Ball, Ph.D., F.G.S., A.R.S.M., Assoc. 

 M.Inst.C.E. 



Inscriptions placed on the rocks at Semna, between the second 

 and third cataracts, under the 12th and 13th dynasties, serve as 

 a means of gauging the local changes due to river-erosion during 

 a period of about 4200 years. Horner, in 1850, came to the 

 conclusion that 



" the only hypotheses which could meet the requirements of the facts observed, 

 would be either the wearing away of a reef or barrier at the place in question— 

 a process requiring too long a period, — or the existence at some distant period 

 of a dam or barrier, formed perhaps by a landslip of the banks, at some 

 narrow gorge in the river's track below Semna.' 



The author is in favour of the former explanation. The river, 



