'226 Geological Society. 



of Charlton Hill, is traced in certain trap rocks which appear in the 

 bed of the Severn, near Cound, extending thence to the south-west. 



Caer Caradoc. — This remarkable ridge, formerly described by 

 Mr. A. Aikin*, is on a line of eruption parallel to that of the Wrekin. 

 It includes the hills of Lawley, Great and Little Caradoc, Helmeth, 

 Ragleath, &c, together with a large contrefort on its south-eastern 

 face. At Cardington and Hope Bowdler it consists of many varieties 

 of felspar rock, sienite and greenstone. The beautiful amygdaloid 

 with actynolite first pointed out by Dr. Townson, and supposed to 

 be peculiar to one spot, is shown to be of frequent occurrence in 

 several of these hills. The axis of elevation of this ridge has been 

 traced by the author to nearly six miles south-west of the limit 

 formerly assigned to it, the trap reappearing at Wartle Knoll, 

 Hopesay, Sibdon, Aston and Corston. 



Numerous examples are adduced of the conversion of sandstone 

 into quartz rock where in contact with the eruptive rocks of these 

 hills, particularly on the south eastern flank of the Lawley, Little 

 Caradoc, and Cardington Hills, the strata of sandstone being 

 thrown off the flanks of the trap rock in vertical and dislocated 

 forms, in some of which the traces of bedding are with difficulty 

 observed. These conversions of sandstone on the sides of the Wrekin 

 and Caradoc Hills are supposed to have been caused by the action 

 of heat, accompanying the forcible intrusion of some of these trap 

 rocks. A large mass of impure limestone, somewhat indurated, and 

 containing many fossils of the Ludlow formation, has been heaved 

 into a vertical and detached position at Botville, on the north- 

 western face of Caer Caradoc. 



Besides these dislocated masses, the author describes a portion of 

 the third formation (May Hill and Horderley), which rises from be- 

 neath the Wenlock shale, contains organic remains, and reposes on 

 the flanks of these trappean hills, as being in structure so analogous 

 to the unstratified rocks themselves, that he terms it '* Volcanic Sand- 

 stone" and conceives that it must have been formed during a period 

 of volcanic action, and that the materials of which it is composed 

 are the residue of ashes given off during submarine ejections. A 

 similar rock is found near the Wrekin. 



Longmynd, Linley, Pontesford, and Haughmond Hills. — The 

 ancient grauwacke system of the Longmynd and Linley Hills, or 

 mineral axis of Shropshire t, is penetrated by a vast number of 

 points of eruptive trap, chiefly greenstones. Pontesford Hill, amid 

 varieties of greenstone, contains also a porphyry and a remarkable 

 amygdaloid. This zone is reproduced at intervals in Sharpstone 

 Hill, and has been observed by the author in Haughmond Hill, 

 four miles north-east of Shrewsbury, where it passes into a coarse 

 sienite. Vertical, veined, and indurated strata appear at different 

 points along these lines of eruption. Copper ores have been par- 

 tially worked on the western sides of the Longmynd, and at Nor- 

 bury. Quartz crystals and small portions of anthracite are found 



* Geol. Trans., 1st Series, vol.i. p. 207- 

 : j, t See our last volume, p. 370. 



