UPPER SECONDARY ROCKS. 9& 
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 da 
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 jloetz or Jlat 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. 
Green Sand and Chalk* 
Oolite Formation and Beds of Clay* 
Lias Clay and Lias Limestone. 
Middle and Upper Red Sandstone and Marif 
with Rock-salt and Gypsum. 
Lower New Red Sandstone and Magnesian 
Limestone* 
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. 
