CONTENTS. 



xvii 



CHAPTER XXIX. 



GEOLOGICAL STRUCTURE OF PEMBROKESHIRE. 

 OVERLYING FORMATIONS. 



Page 



Introduction. — Coal or Culm [Measures. — Millstone Grit. — Carboniferous Limestone. — Old Red Sand- 

 stone. (PI. 35. figs. 1—9.) 370 



CHAPTER XXX. 



PEMBROKESHIRE. 



SILURIAN, CAMBRIAN, AND TRAP ROCKS. 

 Silurian System. — Divided into Upper and Lower Silurian Rocks, with full developments of the Caradoc 

 and Llandeilo formations. — Cambrian System and Slaty Rocks. — Stratification and cleavage coin- 

 cident. — Trap Rocks, bedded and amorphous. — Divergent lines of strike explained by eruptive ridges 

 of trap. (PI. 35. figs. 1, 4, 6, 10, 1 1, 12.) 389 



CHAPTER XXXI. 



MALVERN AND ABBERLEY HILLS. 



Silurian System in Worcestershire and the Eastern part of Herefordshire. — Syenite and other Trap Rocks 

 of the Malvern and Abberley Hills, and dislocations of the Silurian System along their flanks. (PI. 36. 

 figs. 1—8.) 409 



CHAPTER XXXII. 



WOOLHOPE— SILURIAN VALLEY OF ELEVATION. 

 Introduction. — Form of the Valley. — Description of the Silurian Rocks which constitute its encircling 

 ridges and nucleus. — Ancient dislocations which determined its form, fractures, and drainage. — Mo- 

 dern dislocations and landslips. — Drifted matter. (See enlarged Map, p. 427, and coloured sections, 

 PI. 36. figs. 9a., 9b. , and wood-cut p. 429.) 427 



CHAPTER XXXIII. 



SILURIAN GROUPS OF USK AND MAY HILL. 

 1 . Usk Valley of Elevation, consisting, like that of Woolhope, of the Ludlow, Wenlock and Caradoc 

 Formations. (PI. 36. figs. 23, 24.) — 2. Prolongation of the axis of Woolhope, by May Hill to Purton 

 and Tortworth in Gloucestershire. (PI. 36. figs. 11 — 14, 14 bis, 15, 16.) 438 



CHAPTER XXXIV. 



ON THE ROCKS OF THE TORTWORTH DISTRICT (GLOUCESTERSHIRE). 

 General succession of strata, from the Inferior Oolite to the Lower Silurian Rocks. — Inferior Oolite and 

 Lias. — New Red Sandstone and Dolomitic Conglomerate. — Coal Measures. — Carboniferous Lime- 

 stone. — Old Red Sandstone. — Silurian System. — Small development of Ludlow and Wenlock for- 

 mations.— Caradoc Sandstone clearly exhibited. — Trap Rocks all of intrusive character. — Altered 

 and dislocated deposits. — Strata elevated and thrown into anticlinal forms by the outburst of trap. 

 (PI. 36. figs. 16— 22.). 447 



