Geology of Coalhrook Dale. 4 1 5 



being permitted at all times to examine his fine collection of fossils from the coal- 

 measures^ I have been enabled to add considerably to my catalogue of organic 

 remains ; and it was in certain nodules in his cabinet, that I discovered the 

 two impressions, which Dr. Buckland has since shown to belong to coleop- 

 terous insects*. Mr. Anstice's long practical acquaintance with the Madeley 

 coal-field, enabled him also to favour me with many interesting particulars 

 respecting the Madeley and Limestone faults ; and I am indebted to him for 

 the excellent sections of the Madeley Pits. 



I must likewise acknowledge the assistance, which I received during the 

 progress of my inquiries, from the Messrs. Pritchard and Mr. J. Onions of 

 Broseley, Mr. Thomson of Lightmore, Messrs. Darby of the Dale, Mr. 

 Hombersley of Prior's Lee, and Mr. Jones of New Hadley. The ground- 

 bailiffs throughout the whole district, always evinced much civility and readi- 

 ness in accompanying me over their works, and giving me every informa- 

 tion in their power. 



I cannot conclude without expressing my grateful obligations to Mr. Lons- 

 dale, to whose kind suggestions and constant assistance, I feel very greatly 

 indebted. 



Extent and Physical Features. 



The district to be described, is included within an acute-angled triangle, 

 the termination of the zone of Silurian and carboniferous rocks, which ranges 

 through Wales, Herefordshire, &c. This apex of the triangle, near Newport, 

 points about N.N.E.; and its two longer sides, ranging respectively about 

 S.W. and S., are flanked by the new red sandstone. The coal-measures ex- 

 tend from the acute apex of the triangle at Church Aston, near Newport, to 

 Steeraway, a distance of seven miles; and they attain their greatest breadth, 

 34r miles, in the parallel of the latter locality. At this point, the Silurian rocks 

 gradually swell out, and reduce, as we proceed southward, t[ie coal-measures 

 to an irregular and decreasing band, which at Tasley, near Bridgenorth, is 

 only three-quarters of a mile in breadth. The total length of the coal-field 

 from Church Aston to Tasley is 15 miles; its area is about 32 square miles ; 

 and that of the whole district to be described is about 100 square miles. 

 (See Map, PI. XXXV.) 



The surface, occupied by the Silurian and carboniferous rocks within the 

 triangle, is considerably higher than the surrounding country, composed of 

 the new red system. To the east, the surface of this system is undulated 

 * See Dr. Buckland's Bridgewater Treatises, vol. i., p. 409. 



