482 Dr. C. Callaway — Superficial Deposits N. Shropshire. 



of movement. Every stage may be traced, from a long piece of one 

 of the grit bands down to mere rounded and isolated pebbles of 

 the same material. The grits, being much more resisting, have 

 withstood the deformation better than the argillaceous strata, 

 which have been crushed into a kind of lustrous slate, or phyllite. 

 Everywhere the signs of movement or " flow-structure " meet the 

 eye. It is not that the rocks have been merety crushed to frag- 

 ments. The differential movements which produced the ruptures 

 also made the materials to flow onwards, the dislocated bands 

 of grit being reduced to separate blocks and pebbles, entirely 

 surrounded in the moving matrix of finer shaly paste. 



The " agglomei'ates " on the coast near Cemmaes, so singularly 

 deceptive as to be easily mistaken for volcanic necks, prove to be 

 capable of alike interpretation. The huge blocks of limestone, there 

 to be seen isolated among fragmentary grits and slates, are referable 

 to the disruption of some of the limestone bands which occur 

 abundantly in the neighbourhood. A gradation may be traced from 

 the slates and grits outside the areas of more severe dislocation into 

 the intensely crushed and sheared " agglomerate." The dykes 

 which cut through these rocks, and increase the likeness to true 

 "volcanic vents, are later than the period of crushing and may be 

 traced in the surrounding; slates and grits. 



But though the volcanic nature of the rocks believed to be 

 agglomerates must be abandoned, the question of the original 

 formation of the strata which have been so greatly ruptured 

 remains quite distinct. I agree with Mr. Blake in regarding these 

 strata as largely composed of volcanic detritus. The breccias and 

 fine tuffs which alternate with and overlie the Lower Silurian black 

 shales, can be traced upward into the mass of the Amlwch slates, 

 which are full of volcanic dust. The evidence for the existence of 

 Lower Silurian volcanoes in the north of Anglesey remains quite 

 valid and ample, though we must abandon the volcanic origin of 

 the " agglomerates," which seemed to form part of that evidence. 

 The production of the crush-conglomerates has involved the volcanic 

 as well as the non- volcanic parts of the series in the same destruction. 



II. — Notes on the Superficial Deposits of North Shropshire. 1 

 By C. Callaway, D.Sc, F.G.S. 



IN studying the rocks of Shropshire, I have paid some attention 

 to the superficial deposits that lie irregularly scattered over 

 the solid strata in the northern half of the county. They had 

 previously been noticed by Miss C. Eyton, in her little book " On 

 the Geology of North Shropshire," while special areas occupied 

 by them have been described by Mr. G. Maw, Mr. C J. Woodward, 

 and Mr. A. C. Nicholson. Nevertheless; it seemed to me that it 



1 A brief abstract of this paper was read before tbe British Association, 

 Liverpool, 1896. 



