DESCRIPTION OF THE SECTIONS. 



721 



Highly altered rocks are seen on the flanks of the trap Trafgarn j and near that of Johnston 

 the Carboniferous Limestone is in an inverted position, appearing to overlie the coal-measures. 



Fig. 2. From Milling to Williamston, showing in the northern half of the section a regular de- 

 scending series of the younger formations, from the productive coal or culm seams, to the Car- 

 boniferous Limestone inclusive, and in the southern half the same strata contorted, broken and 

 reversed, with a mass of eruptive trap which pierces the Old Red Sandstone. 



Fig. 3. Relations of Lower Coal Measures to Silurian Rocks at Slebech. See p. 372. 



Fig. 4. Succession of strata from the north of Narbeth to Amroth, showing the full development 

 and regular order of all the formations from the Silurian System to the culm measures inclu- 

 sive. See pp. 372, 390. 



Fig. 5. Section similar to f. 4. in exhibiting the succession from the Old Red Sandstone to the 

 coal measures, with a full development of the Carboniferous Limestone and Millstone Grit, but 

 differing in showing a break between the Silurian Rocks and the Old Red Sandstone. The 

 upper Silurian Rocks are entirely omitted, while the Llandeilo Flags are very largely ex- 

 panded near Llampeter-felfrey. See pp. 396 et seq. 



Fig. 6. Passage from the Old Red Sandstone to the Silurian Rocks near Tavern Spite (Cynic) in 

 the eastern extremity of Pembrokeshire, with a. fine exhibition of the limestone of the Llan- 

 deilo Flags at Clog-y-frain, in the adjacent county of Caermarthen. 



The River Taaf flows in a gorge formed by the great transverse dislocations of the Lower 

 Silurian Rocks. See pp. 358, 396. 



Fig. 7. Coast section of the central portion of St. Bride's Bay, showing the contortions and frac- 

 tures of the culm measures, and how they rest in some places upon Millstone or Coal Grit, 

 and in others upon Silurian and Cambrian Rocks. 



The central or dotted portion represents the lower and unproductive coal grits and sand- 

 stones, which are prolonged to Haroldston's Nose from the Poor Field near Haverford-west. 

 See p. 373 et seq. 380. 



Fig. 8. Relations of the culm beds at Norton to the Lower Silurian Rocks, showing very little un- 

 conformability between them. See pp. 375, 377* 



Fig. 9. Relations of culm measures and underlying sandstones and grit to Cambrian Rocks, show- 

 ing, like f. 8., very little unconformability. At Brawdy, on the contrary, culm rests on Mill- 

 stone Grit, which is unconformable to the Cambrian Rocks. See map, and pp. 375 et seq. 



Fig. 10. Great transverse coast section of the Silurian System as exposed in Broad Sound (prin- 

 cipally in Marloes Bay) from the Old Red Sandstone on E.S.E. to the Cambrian Rocks on 

 the W.N.W., showing the regular emergence of the Ludlow, Wenlock, Caradoc, and Llan- 

 deilo formations. Intrusive trap bursts through the Upper Silurian Rocks (junction of Wen- 

 lock and Ludlow) in Marloes Bay ; trap rocks, both interstratified and intrusive, alternate with 

 the Cambrian Rocks of Skomer Island and the adjacent promontory. A slaty cleavage prevails 

 throughout the Lower Silurian Rocks, and is partially seen in the upper. See pp. 392 et seq. 



Fig. 11. Coast section of the Llandeilo Flags, in Musclewick Haven, Marloes ; showing their un- 

 conformable junction with the Old Red Sandstone. Slaty cleavage traverses these flags ob- 

 liquely. Faults are marked in the Old Red Sandstone. Eruptive trap overflows the Llan- 

 deilo Flags. See p. 394. 



