102 UPPER SECONDARY ROCKS. 
of them now present ; so that we have here, also, 
decisive evidence that they have been elevated sub- 
sequent to their deposition." 
Oolite, 
The rocks lying immediately above the new red 
sandstone are called the oolitic. They derive their 
name from the small rounded globules that are im- 
bedded in them; and as these sometimes resemble 
the roes of fish, the rock is called roe-stone. This 
formation abounds on the Continent of Europe, and 
particularly in England ; although we meet with 
limestone rocks in this country which have an oolitic 
structure, it is yet in dispute whether they are ex- 
actly equivalent to the European oolite, either as 
respects their relative position or their organic re- 
mains. According to Conybeare and Philips, the 
oolitic group may be divided into three series, each 
of which is composed of three distinct formations, 
viz., an oolitic rock, a calcareous sandstone, and ^marL 
The oolite rocks are distinguished as upper, middle, 
and lower, and occupy, in England, a zone which is 
nearly 30 miles in average breadth, and extends 
across the island from Yorkshire on the northeast 
to Dorsetshire on the southwest. These again are 
subdivided into several varieties, such as Portland 
stone, Kimmeridge clay. Coral rag, Oxford clay, &c. ; 
and below the whole is situated the formation called 
lias. This term is derived from the provincial pro- 
nunciation of the word layers ; as the strata of lias 
limestone are generally very regular and flat, and 
can easily be raised in slabs from the quarry. When 
the lias beds are fully developed, with their associ- 
ated beds of clay, they form a mass of stratified 
limestone and clay several hundred feet in thick- 
ness, which rests upon the red marl described in 
the last chapter. This lias limestone is of a dark 
gray or yellowish white colour ; argillaceous ; divi- 
ded into thin strata of an earthy, marly texture, and 
