Geology of England and TVales, &/-c. 209 



prehends the three first orders in the preceding table. 

 Those in the Superior Order embrace all above the chalk; 

 viz. the Alluvial and Diluvial ; the Upper Marine Forma- 

 tion ; the Fresh Water Formations; the London Clay, and 

 the Plastic Clay The Supermedial Order comprehends 

 the Chalk; Beds between the chalk and Oolitic Series; the 

 Ooliiic Series; and the formations between the Lias and coal. 

 The Medial Order embraces the Independant Coal Form- 

 ation of Werner; viz. the Coal Measures; the Mill- 

 stone Grit and Shale; the Carboniferous or Mountain 

 Limestone : the Old Red Sandstone, and the Trap Rocks 

 occurring occasionally in the coal fields. 



The mode of description, adopted in this work, is sys- 

 tematic in a high degree. The different orders are divided 

 into several distinct series, and these, into many species or 

 varieties. In entering upon a description of these orders 

 and series, we have first presented a general view of the 

 formation, not only in England, but also in other countries. 

 The writers next proceed to describe the different species 

 and varieties ; adopting in most instances, the following di- 

 vision for each : a chemical and external characters ; b 

 mineral contents; c organic remains ; d range and extent ; e 

 height of hills, &c./ thickness, he. g inclination he. h agri- 

 cultural character ;^phenomena of springs and wells in this 

 formation. Other particulars are sometimes added, and often, 

 some of the above are omitied. After the description, em- 

 braced under these heads, is finished, local details, concern- 

 ing the formation, are frequently subjoined; often embra- 

 cing important additional facts. There are many obvious 

 advantages attending such a mode of description : but for 

 some reason or other, in the work before us, it has often 

 cost us considerable labour, to obtain a complete and dis- 

 tinct view of a formation. 



We now proceed as proposed, to give a short sketch of 

 the English formations as exhibited in the work before us; 

 beginning with the Superior Order. 



Alluvial. This formation embraces only those deposi- 

 tions, that result from causes still in operation. The princi- 

 pal agent employed in its production is rivers; but the 

 sea, rain, frost, wind, vegetation, he. exert also a very small 

 influence in modifying the face of the globe. Those coral 

 reefs and islets, formed by the labours of " millions of ma- 

 V^oL.VlI.~No, 2. 27 



