248 Rev. James Yates on the Structure of the 



eastern border, we seem to be amidst the vast ruins of a former world : In 

 Caer Caradoc, the most celebrated of these hills, we may trace two great dykes 

 of stratified clay-stone. They rise in numerous ragged precipices above the 

 summit of the hill, and in their forms, though not in their mineralogical qua- 

 lities, they resemble the before-mentioned fragments of inverted strata, which 

 crown the Stiperstones. 



At the bottom of Caer Caradoc and at its N. E. extremity we find again the 

 same quartz-rock as that of Bromsgrove Lickey, in nearly vertical strata. 

 From a crystalline state it passes into that of a coarse sandstone, the grains of 

 which are rather loosely aggregated ; a vein of trap, about 12 inches thick, 

 passes through the sandstone. 



In ascending Lawley Hill above the village of Comely, we again find the 

 quartz-rock near the base of its southern declivity. An excavation has disco- 

 vered in it an irregular space filled with quartz-pebbles and sand, which are 

 rather loosely cemented with clay. This inclosed mass is divided into angular 

 concretions, with a siliceous cement bounding each concretion, and entering 

 more or less into its substance. We may suppose that the sand and pebbles 

 were first united by a loose cement of clay, and that, as the clay hardened, the 

 entire mass formed itself into its separate concretions ; the clay having pre- 

 vented the free entrance of fluids, the interior of the concretions is devoid of 

 any subsequent addition. But the fluid which contained the sihceous matter of 

 the adjoining quartz-rock has penetrated between the concretions, and for some 

 depth into them. The surfaces of the concretions sometimes exhibit the stri- 

 ated appearance of the slickensides of Devonshire and Corn^vall, which has 

 been commonly attributed to the supposed sliding of one mass of rock over 

 another ; but in the case before us, and in that already noticed at Llanvorda, 

 the striae are evidently the result of crystallization. 



The quartz-rock both here and at the base of Caer Caradoc, contains small 

 portions of malachite, and indeed this substance characterizes the rock where- 

 ever I have found it. Ascending Lawley Hill, at a situation higher than the 

 quartz-rock, we again meet with the trap, containing, as on the opposite decli- 

 vity of Caer Caradoc, globular concretions of radiated epidote. 



Lawley extends from north to south in a narrow ridge, which may be re- 

 garded as a continuation of that of Caer Caradoc. The two extremities of 

 the ridge have a slight, though very perceptible convergence towards the 

 west ; thus the hill assumes something of a crescent form, which may be ob- 

 served in like manner in most of the trap hills of this region : on the east it is 

 encompassed by a valley of considerable depth, which is terminated by a sharp 

 ridge, somewhat tortuous in its course, and consisting of a fine white crystal- 



