

Glamorganshire, 





Feet. 



Coal-measures . 



. . 11,650 



Millstone Grit . 



3 



24 Original Articles. [Jan. 



South of the Barrier. 



Forest of Dean, 



Gloucestershire. 



Feet. 



2,765 

 455 



11,980 3,210 



From the above examples it will be observed that between Lanca- 

 shire and Leicestershire there is a falling off, in a distance of about 

 seventy miles, of about 10,000 feet of strata, and between Glamor- 

 ganshire and Gloucestershire, in a distance of about fifty miles, a 

 falling off of about 8,000 feet. Similar results might be obtained by 

 comparisons along parallel lines of country. 



The question may now be asked, " What does this prove ? " The 

 answer, I think, is plain ; it proves the gradual dying out of the coal- 

 formation towards the Eastern Counties, and affords grounds for the 

 belief that even if there had existed no barrier of land in this part of 

 England, the formation would have failed to extend itself under the Cre- 

 taceous districts. The Barrier has, however, formed the termination of 

 the northern coal-area towards the south-east, as well as of the 

 southern coal-area towards the north-east, in both instances more 

 abruptly than would have resulted from the mere thinning out of the 

 beds ; on these grounds I have left unshaded the part of the map form- 

 ing the Eastern Counties.* 



3. Tlie Distribution of the Formations overlying the Carboniferous. 



We now approach the third topic of our inquiry, and in doing so 

 shall limit ourselves to the Permian, Triassic, j and Jurassic J forma- 

 tions. The lowest member of the Permian formation (the Rothe-todt- 

 liegende) is extremely variable, and seems to have been deposited in a 

 depression formed in the Carboniferous beds of which Warwickshire 

 may be considered the centre. Here it reaches a thickness of 2,000 

 .feet, and thins away from this centre in every direction. The upper 

 member, or magnesian limestone, is for the most part confined to the 

 north-east of England. Coal may be considered as within workable 

 reach whenever it occurs under the Permian formation, provided this 

 latter forms the surface of the ground, and the depth will not exceed 

 1,000 yards. 



When we come, however, to consider the distribution of the form- 

 ations which succeed the Permian, we cannot but be struck with the 

 regularity of the plan upon which they have been formed. We have 

 already seen the manner in which the Carboniferous strata increase 

 and decrease in certain directions. Now it has been found, on com- 

 paring a series of carefully-measured sections and tracing the sub- 

 divisions of the Triassic group, that they undergo a like decrease in 



* I may again refer to the Harwich horing, which in a remarkable degree cor- 

 roborates the above inferences. 



t Triassic— comprehending new red sandstone and marl. 

 X Jurassic — tho*e of the lias and oolite. 



