Correspondence — Br. C. Callaivay. 377 



The paper also gives further information concerning tlie Bajocian 

 denudation, and with it is presented a map showing the areas of 

 the different rocks upon which the Upper Trigonia-gxit reposes 

 non-sequentially. Notice is also taken of a water-bearing bed, and 

 of its economic importance. Some remarks are made upon the 

 ancient geography of the Cleeve Hill plateau in regard to streams. 

 Their probable courses are marked upon a map. 



3. " Pleistocene Plants from Casewick, Shacklewell, and Grays." 

 By Clement Keid, Esq., F.L.S., F.G.S. 



The i)lants from Casewick and Shacklewell were obtamed by 

 washing two lumps of clay in the collection of the late Sir Joseph 

 Prestwich. The species are few and call for little remark, except 

 that the climate was not Arctic. They are all common British 

 forms. 



The collection from Grays consists of leaves, already partly 

 determined by Gaudin and Heer, though unpublished, and some 

 lumps of clay, out of which the author washed a few seeds. The 

 flora points clearly to a temperate climate and mild winters. 



4. "An Explanation of the Claxheugh Section (Co. Durham)." 

 By D. Woolacott, Esq., M.Sc. (Communicated by Professor G. A. 

 Lebour, M.A., F.G.S.) 



The section of which an explanation is offered in this communi- 

 cation occurs about two miles west of Sunderland, and has been 

 noticed by Messrs. King and Howse and Professor Lebour. The 

 base shows the Permian Yellow Sands, which are succeeded at the 

 west end of the section by the Marl Slate, thin-bedded limestones, 

 and at the top crystalline limestones without any trace of bedding. 

 At the east end the Marl Slate and thin-bedded limestone are absent, 

 and, except when a breccia intervenes, the crystalline limestone rests 

 on the Yellow Sands, though the thin-bedded limestone and Marl 

 Slate show no signs of thinning-out. There are also minor compli- 

 cations. The author suggests that the section may be explained by 

 supposing that denudation occurred in a cavern, the roof of which 

 afterwards fell in, and that disturbances were also produced by 

 " creep "-movements. 



THE ORIGIN OF THE GEEY GNEISS OF ANGLESEY. 



Sir,— In the debate at the Geological Society on April 28, when 

 my paper on the Grey Gneiss of Anglesey was read, some criticisms 

 were offered by the Kev. J. F. Blake, to which, with your per- 

 mission, I desire to make a brief reply. Had I enjoyed the good 

 fortune to be present on the occasion, it would not be necessary tor 

 me thus to trouble you. 



To save your valuable space, I will confine myself to one point. — 

 the nature of the rock out of which the grey gneiss has been formed. 

 This is a vital part of the question, and, if it be settled, much else 

 will follow. In my paper I contended that the gneiss was originally 



