496 



THE WONDERS OF GEOLOGY. Lect. V. 



The Lias forms a district that lies parallel with the 

 escarpment of the oolite, from beneath the base of which it 

 emerges ; it traverses the country from the well-know 7 ? 

 cliffs at Lyme Regis in Dorsetshire, to near Redcar, on the 

 Yorkshire coast. 



9. Railway sections. — In a previous lecture (vol. i. p. 

 363) we described the sections presented by the south-eastern 

 railway, as affording a coup-d'oeil of the geological struc- 

 ture of that part of England : in like manner the lines that 

 traverse our Island in other directions enable the instructed, 

 observer to obtain a general idea of the geographical distri- 

 bution and position of the principal groups of the rocks 

 and strata. 



More than a quarter of a century since, the information 

 to be derived from such a survey was admirably pointed 

 out by Mr. Conybeare.* "If," observes that eminent 

 geologist, " we suppose an intelligent traveller taking his 

 departure from the metropolis, to make from that point 

 several successive journies to various parts of this Island, 

 for instance, to North or South Wales, or to Cumberland, 

 or Northumberland, he cannot fail to notice (if he pays any 

 attention to the physical geography of the country through 

 which he passes) that before he arrives at the districts in 

 which Coal is found, he will first pass a tract of clay and 

 sand ; then another of Chalk ; that he will next observe 

 numerous quarries of the calcareous freestone used in 

 architecture ; that he will afterwards pass a broad zone of 

 red marls and sands, and beyond this will find himself in 

 the midst of coal mines and iron furnaces. This order he 

 will find to be invariably the same, whichever of the 

 routes above indicated he pursues ; and if he proceeds 

 further, he will perceive near the limits of the coal fields, 

 hills of compact limestone, affording grey and dark marbles, 



* Geology of England and Wales, p. ii. 



