44 ReporU and Proceedings — 



crust as affecting the succession of the rocks in that area. The sup- 

 posed continuous upward succession from the rocks on the shore of 

 the Bristol Channel to those in the neighbourhood of Barnstaple, 

 including, according to some authors, no less than ten groups, and 

 classed into three divisions under the names Lower, Middle, and 

 Upper Devonian, is, the author believes, an erroneous interpretation. 

 The beds, he says, have been greatly plicated and faulted, and con- 

 sequently several times repeated, and instead of being one continuous 

 series, they occur folded in more or less broken troughs. In the 

 Morte Slates, previously considered unfossiliferous, the author found 

 a Lingula, and he believes that these slates are the oldest rocks in 

 the area, and formed the floor upon which the Devonian Eocks were 

 deposited unconformably. As the result of movements in the Earth's 

 crust, the Morte Slates have been brought to the surface and thrust 

 over much newer rocks, producing a deceptive appearance of over- 

 lying the latter conformably. The Morte Slates mark the dividing 

 line between the two main troughs. On the north side in ascending 

 order are the Hangman (or Lynton), Combe Martin Bay, and Ilfra- 

 combe Beds, and on the south side the Pickwell Down, Baggy Point, 

 and Pilton Beds. Those on the south side of the Morte Slates are, 

 the author believes, a repetition of the beds on the north side. The 

 palseontological evidence is not antagonistic to this view, for an 

 analysis of the Brachiopoda, the only group of fossils in the beds on 

 the south side, which hitherto have been systematically examined, 

 shows that of the twenty species mentioned by Mr. Davidson and 

 others as occurring in the Pickwell Down, Baggy Point, and Pilton 

 Beds (the so-called Upper Devonian rocks), no less than thirteen 

 have already been found in the Middle or Lower Devonian rocks on 

 the north side of the Morte Slates. Four others are recognized 

 Middle Devonian species in other areas ; and the three remaining 

 are either doubtful species or ones which have a great vertical range. 

 These facts show that the so-called Upper Devonian rocks in this 

 area do not contain a distinguishing fauna of any importance : and 

 the stratigi'aphical evidence is opposed to the view that they are 

 a series of rocks distinct from those on the north side of the Morte 

 Slates, which have been classed as Middle and Lower Devonian. 



Ill— December 10, 1890.— Dr. A. Geikie, F.R.S., President, in 

 the Chair. — The following communications were read; — 



1. " On some Water- worn and Pebble-worn Stones taken from 

 the Apron of the Severn Commissioners' Weir erected across the 

 Eiver at Holt Fleet about eight miles above Worcester." By Henry 

 John Marten, Esq., M.Inst.C.E., F.G.S., etc.. Engineer to the Severn 

 Commissioners. 



The Weir referred to in the paper was built in 1844 of soft red 

 sandstone, and some of the stones composing the apron of the Weir 

 showing signs of decay were removed in 1887. The average quan- 

 tity of water passing over each square foot of the stones composing 

 the apron has been estimated at about 2000 gallons per minute. A 



