CONTENTS. 



xv 



CHAPTER XV. 



OLD RED SYSTEM {continued). 



Trap-Dykes in the Old Red Sandstone ; Mineral Veins ; Dislocations ; Outliers ; Agricultural Characters 



of the Old Red System 185 



CHAPTER XVI. 



SILURIAN SYSTEM. 



Introduction. — Upper Silurian Rocks. — 1st Formation or "Ludlow Rocks." (PI. 31. figs. 2 — 5.) .... 195 



CHAPTER XVII. 



UPPER SILURIAN ROCKS {continued). 

 2nd Formation or " Wenlock Limestone." (PI. 31. figs. 2 — 5.) , 208 



CHAPTER XVIII. 



SILURIAN SYSTEM {continued). 

 Lower Silurian Rocks —3rd Formation or " Caradoc Sandstone."— 4th Formation or "Llandeilo Flags." 



(Plates 31, 32, 34.) 216 



CHAPTER XIX. 



SILURIAN SYSTEM {continued). 

 Trap and altered Rocks of the Caradoc, Wrekin, &c. — Periods of Volcanic Eruption. — Dislocations and 



Outliers of Silurian Rocks. (PI. 31. figs. 3, 4. PI. 32. f. 1.) 225 



CHAPTER XX. 



SILURIAN SYSTEM {continued). 

 Joints of the Silurian Rocks.— Landslips.— Wells. — Agricultural characters of the Silurian System 243 



CHAPTER XXI. 



CAMBRIAN SYSTEM. 

 PART OF THE UPPER GROUP. 

 Mineral Axis of Shropshire.— Cambrian and associated Trap Rocks in the Hills of Longmynd, Ratling- 

 hope, Linley, Pontesford, Lyth, and Haughmond. (PL 31. f. 4. PI. 32. figs. 1, 2 and 4. PL 33. f. I.) 255 



CHAPTER XXII. 



LOWER SILURIAN AND TRAP ROCKS, LEAD ORES, QUARTZ ROCK, &c. 



Lower Silurian Rocks alternating with Volcanic Grits (Shelve, &c.).— Amorphous or Intrusive Trap 

 (Corndon, &c). — Altered Rocks and Veins of Lead. — Quartz Rock of the Stiper Stones. (PI. 32. 

 figs. 1, 2, 3.) 268 



