498 GEOLOGY. 



tion, there are alternations of beds of oolite limestone, shelly lime- 

 stone, calcareous sandstone, various marls, clays, and fuller's earth. 

 It rests upon the second or new red sandstone. 



" 6. Third Sandstone Formation , or the Green Sand Formation. 

 This formation extends through a large portion of the south-east- 

 ern parts of England. Its characteristic member is a siliceous sand- 

 stone, abounding in grains of a substance resembling green earth or 

 augite. Besides this sandstone, the formation contains beds of a 

 coarse shelly limestone, of various clays, fuller's earth, and of iron 

 sand. It rests upon the third limestone or oolite formation. 



" 7' Fourth Limestone Formation, or Chalk Formation The 



lower part of this formation is composed of a gray clayey chalk, 

 without flints, and of gray-coloured clays and marls. Immediately 

 above is a hard chalk, with few flints, and above is the softer chalk 

 in which flints and organic remains abound. 



" 8. Brown Coal Formation In this formation, which appears 

 to rest upon chalk, brown coal occurs in great masses, associated with 

 clays and marls, and occasionally with glance coal. The English 

 pudding-stone appears to rest immediately, either on the brown coal 

 or the chalk formations. 



9. Paris Formation Under this head we include the series of 

 beds of clay, marl, limestone, gypsum, sand, and sandstone, that oc- 

 cur in the basin of Paris, and also in that of the Isle of Wight and 

 other quarters. They lie above chalk, and higher than the brown 

 coal, and are divided into sets ; two characterized by the presence 

 of fresh water shells, and remains of quadrupeds, are named fresh 

 water formations ; and other two, containing principally salt water 

 shells, are named marine formations. 



(e 10. Secondary Trap Rocks The rocks of this division have 

 been described by many geologists as lavas. They occur in imbed- 

 ded masses, beds and veins, in many of the formations already de- 

 scribed, and hence, in order to prevent repetition, we have brought 

 them together under one division. They are principally composed 

 of augite, with occasional hornblende and felspar ; the augite occurs 

 in all its states from the crystalline to the earthy or powdery con- 

 dition, and the felspar appears in all the different states from clay- 

 stone and clay to the crystalline state. The following are the se- 

 condary trap rocks : Basalt, greenstone, syenite, amygdaloid, porphy- 

 ry, and tuffa." 



IV. ALLUVIAL STRATA. The various clays, loams, marls, 

 sands, gravels, rolled masses, &c. which He over the more solid 

 rocks, are included in this division. They are divided into two 



