UPPER SECONDARY ROCKS. 97 
the tertiary group, or those lying above them, not 
only by their chemical character^ being chiefly creta- 
ceous (carbonate of lime), but by their greater com- 
pactness; a want of conformity in their strata (the 
secondary being rarely parallel to those of the su- 
perior order), and also, as has been already stated, 
by a great difference in their organic remains. The 
formations which fall under this group may then 
briefly be described in the following order in the as- 
cending series : 
1. New Red Sandstone. I 2. Oolitic, 
3. Green Sand, \ 4. Cretaceous or Chalk. 
The new red sandstone is so called to distinguish 
it from that found among mountain rocks, called 
old. Its prevailing character is silicious, but it of- 
ten comprises calcareous beds of considerable ex- 
tent. Bakewell divides this rock into three series, 
viz. , the upper, the middle, and the lower beds. These 
divisions are often well marked by intervening beds 
of limestone ; where such do not occur, they are so 
blended as to be undistinguishable. It is the general 
opinion of geologists, that this rock, together with 
the conglomerate beds found in it, was formed by 
the violent disintegration of the older rocks, and par- 
ticularly of trap rocks, that were protruded at the 
era of some great convulsion, which broke down a 
large portion of the ancient crust of the globe, and 
spread the debris far and wide over the bed of the 
existing ocean. This appears from the fact that 
fragments of the older rocks occur in the diff*erent 
beds of this sandstone, and that some of the beds 
are almost entirely formed of such fragments. This 
mode of formation is supposed to account for the 
great diversity both in the nature and thickness of 
the beds in different districts. Some geologists 
maintain that the disintegrating causes which broke 
down part of the ancient rocks, and thus spread 
abroad their ruins, acted at successive periods of 
