B. Jones — On the Carboniferous Deposits of Shropshire. 369 



Another law wliicli prevails is that the distance from the Penny- 

 stone to the Best Coal is increased as we proceed from North to South, 

 as will best be shown by the following measurements in the several 

 sections there mentioned : — 



ft. in. 



Granville Pit 16 2 



Lodgewood 22 9 



Wombridge 22 6 



Lawley New Works 30 6 



Little "Wenlock 17 6 very much to the West. 



Lightmoor 34 5 



Castle Trial Pit 47 4 



Lodge Pit, Madeley 60 5 



Meadow Pit, ditto 65 6 



Yew Tree Pit (Calcut Field) 74 



The distance from North to South over which these observations 

 are made is about six miles. Now suppose the Coal-field, instead 

 of being cut off by Symon ground (i.e., denudation)^ to the south o f 

 Caughley, was continued, say as far as Harcott, which is still 

 further south about 12 miles, did this law still prevail the distance 

 between these two horizons of Penny -measures and Best Coal would 

 be so much more increased. Indeed, the argument would be that, 

 as in six miles the thickness had increased 58 feet, it would be 

 increased by 116 feet more at 12 miles further south, and as the 

 total thickness at the Yew Tree Pit is 74 feet, at Harcott it would 

 be 74 -f 116 = 190 feet. 



I hope, presently, to show that this is approximately the case, as 

 proved by the Harcott section, which is sunk through what I believe 

 to be a patch of the older Coal-measures, which, like Shirlot, Brown 

 Clee, and Cornbrook, are islands of Coal-measure which have escaped 

 'the denudation by which they have been isolated from the parent 

 field. In the first place we will see how far the Lower Coals of 

 Harcott compare with those in the Southern part of the Coalbrook- 

 dale field. Before I had discovered that there was any relationship 

 between the Clee Hills and Harcott, I had seen that they were 

 undoubtedly the representatives of the Best, Eandle, Clod, and Little 

 Flint Coals of Coalbrook-dale. It will be observed that Ironstones 

 set in between the Clod and Little Flint Coal south of a line 

 drawn, say from Ironbridge to Cuckoo Oak. There we have them 

 described as " Clod Coal Pennystone " and " Large nodules of Iron- 

 stone." It would appear, then, that as we proceed southward, not 

 only do the changes before mentioned take place, but this new 

 feature sets in, and is not only maintained, but considerably increased, 

 as shown in the Harcott section. The following sections are from 

 Hills Lane Pit, the Meadow Pit (Madeley), and Amies in the 

 Coalbrook-dale district. 



Meadow Pit. — Section D. ft. in. 



1. Best Coal 2 8 



2. Clod {very hard), 1ft. 8in., Clod (very soft) 2ft. lOin 4 6 



3. Middle Coal (very indifferent) 2 8 



4. Clod 10 



5. Clod Coal (very good) 1 10 



6. Pricking, 7in., Poundstone, 2ft. lin 2 8 



7. Little Flint, Coal Flint, very hard and full of large Ironstone 13 10 



8. Little Flint Coal 3 4 



9. Crawstone measure and Crawstone 2 5 



10. Coal under Crawstone 6 



1 Vide Geol. Mag., May, 1871, Outhe Denudation of the Coalbrook-dale Coal-field. 



VOL. VIII. — NO. LXXXVI. 24 



