UPPER SECONDARY ROCKS. 



95 



4. Chalk. It is in this formation that we find the 

 bones and entire skeletons of enormous reptiles, but 

 few of the mammiferous land quadrupeds. The 

 secondary rocks abound in marine shells, and fos- 

 sil vegetables are sometimes found in them, but not 

 abundantly. Secondary strata cover a large por- 

 tion of the habitable globe, and furnish some of the 

 most fertile districts to the agriculturist. This class 

 of rocks contain neither metallic veins nor metallic 

 beds deserving notice (except iron ores), nor do 

 they furnish any rare species of crystallized min- 

 erals. They furnish, however, rock-salt and gyp- 

 sum, and it is from them that nearly all our salt- 

 springs issue. Some of the rocks in this class yield 

 useful building materials, but the stone is generally 

 soft and perishable. The secondary rocks were 

 called by Werner fioetz or flat rocks, because in 

 the northern parts of Europe they are generally ar- 

 ranged in a horizontal position ; but this character 

 being found not to belong to the same class of rocks 

 in other countries, the term has gone out of use. 



Section of the Upper Secondary Rocks of England. 

 Fig. 29. Soil. 



1. Green Sand and Chalk. 



2. Oolite Formation and Beds of Clay. 



3. Lias Clay and Lias Limestone. 



4. Middle and Upper Red Sandstone and Marl, 



with Rock-salt and Gypsum. 



5. Lower New Red Sandstone and Magnesian 

 Limestone. 



6. Upper Transition Rocks and Coal Measures* 



* In the sections above given, we have the strata represented 

 in a perpendicular position, for the sake of convenience, and to 

 fix their relative situation more clearly in the mind of the reader. 



