SUCCESSION AMONG ROCKS. 289 



This complicated series, the next in order when 

 present, is often of an enormous depth, consisting of 

 sandstone, shale, clay, and limestone, with inter- 

 mediate beds of coal and with vegetable remains. 

 This collection of strata appears less consistent as 

 well as less constant than most of the principal series ; 

 being distributed in distinct situations which, from 

 the discrepancy in the recurrence of the several beds, 

 appear to have been in a great measure independent 

 of each other. 



Thus far, the general dips or positions of the beds 

 are marked by the same kinds of irregularity which 

 attend the primary strata. They are commonly much 

 inclined, and sometimes reversed and dislocated ; 

 although, taking a considerable tract, there may be 

 a prevailing dip as well as a prevailing direction. The 

 coal series is particularly noted for its irregularities 

 of this nature. Beyond this point, however, a new 

 arrangement appears to commence ; and the strata 

 which follow, maintain a parallel order to each other, 

 with certain local exceptions that will be noticed in 

 their proper places; while they are, at the same time, 

 much more regular, and less subject to high angular 

 positions. This new order is analogous to that 

 which occurs between the primary and the secondary 

 classes, while it is generally more, strongly marked. 



Where the series is most complete, the coal strata 

 are followed by the rnagnesian limestone, as it is 

 called, or by a conglomerate formed of fragments of 

 the lower calcareous rock and others, cemented by 

 that substance. To this succeeds the very important 

 stratum to which, in England, is given the name of 

 new red sandstone or red marl. 



The red marl is not however a simple substance ; 

 but is in itself a complicated series, consisting of 



VOL. I. IT 



