710 KKroRT— 1892. 



planes, in wliicli either {(i) breccias, or (6) mere fine chloritic debris, rendered 

 crudely fissile in the presence of water by pressure, have resulted from large and 

 small dislocations, to which the mouutaLn-mass has been subjected at various 

 periods of its history. 



The author's general conclusions are : — 



1. That the prevalent petrological morphology of the Malvern crystallines is 

 diagenetic, rather than due to subsequent metamorphism. 



2. That the geotectiuiic features, due to the action of purely mechanical forces, 

 are mainly of a metataxic nature, and that such forces have been very limited in 

 their action in altering the atomic relationships of the chemical constituents of 

 the rocks. 



3. That the most important problem the Malvern crystallines still present to 

 the investigator is the determination of the limits of action of dynamic forces, and 

 of original segregative action by atomic movement (supplemented by the differen- 

 tial action of gravity upon minerals of different density in the primordial magma, 

 aided perhaps by forces of a tidal nature upon the magma as a whole) in bringing 

 about the structural phenomena presented by the Malvern crystallines. 



4. These phenomena seem to lend no suppoi't to the doctrine of ' regional meta- 

 morphism,' as usually understood, for they seem to admit of easier explanation as 

 the results of deformation of originally crystalline masses, rather than of recon- 

 struction out of elastic materials. 



7. The Igneous Hocks of the Neighbourhood of Builth. 

 By Henry Woods, B.A., F.G.8. 



An account of the geology of the Builth district was given by Murchison in the 

 ' Silurian System ' (1839), since which date scarcely anything has been written on it. 

 A series of igneous rocks associated with beds of Ordovician age stretches from 

 near the town of Builth to beyond Llandrindod. Tn this paper the author con- 

 fined himself to the southern half of this area, giving a preliminarv description of 

 the distribution and characters of the rocks met with, namely, diabase, rhyolite, 

 porphyrite, andesite, and ashes. 



8. Note on a Green Sand in the Lower Greensand, and. on a Green Sandstone 

 in Bedfordshire. By A. C. G. Camerox, Geological Survey of England 

 and Wales. 



The beds in the section at the ' Parish Sandpit ' at Aspley Guise are given 

 below, in descending order. 



1. Yellow and grey sand with strii-:gs of yellow fullers' earth . 



2. Lenticular seam yellow fullers' earth . . . 6 ft. to 



3. Yellow and grey sand, in parts false-bedded 



4. Yellow fullers' earth, dovetailed amongst green sand . 

 .5. Yellow ochre ........ 



6. Bright green .sand, ' hearted ' darker green . 



7. Coarse, buff-coloured irony sand ..... 



Oxford clay 



The bright green sand (No. 6), with a darker middle portion, consists of irre- 

 gular-shaped grains of quartz, stained green ; besides which, there are brown 

 errains, the precise nature of which remains for the present undetermined. With 

 the hammer this sand gives a brown streak, the brown grains, which are compara- J 

 lively soft, being the cause of it. The absence of glauconite is a distinct feature! 

 in this sand, that being the usual colouring matter of cretaceous green sands. Aj 

 darker tint of green pervades the middle portion of the bed, giving it the appear- 

 ance of being ' hearted,' as the expression goes. Rather over a mile from this] 

 place, Mr. Whitaker observed in the tower of Husborne Crawley Church a quan- 



