31 



Company, 418 yards; Ffochrhiw (Bargoed Eumny) Dowlais Company, 435 

 yards; Castle Pit, Cyfarthfa (Taff VaUey) Eobert Crawshay, Esq., 332 yard ; 

 Navigation Colliery (Aberdare) Messrs. NLxon and Co., 420 yards; Dinas 

 Colliery (Rhondda VaUey) Messrs. Coffin and Co., 403 yards ; Llwyn-y-pia 

 (Rhondda VaUey) Glamorgan Coal Company, 382 yards ; Blaen Rhondda 

 (Rhondda VaUey) Messrs. J. Marychurch and Co., 402 yards. 



The section appended is compiled from sinkings and workings in the Tatf 

 VaUey. 



The upper part commences at the top of Messrs Bookers' Pentyrch, 

 Rhyd-yr-heUg Pit, which would be the highest ground geologicaUy of any 

 between Pontypool and the Vale of Neath, and passes through the Upper 

 Lantwit coals untU the principal seam, known as the MynyddisU^vj-n or 

 Lantwit coal, is met at a depth of 176 yards. This is a very superior coal, and 

 the best for house and gas purposes in the field ; it is worked along the high 

 grounds near Pontypool, Blackwood, GeUigaer, Caerphilly, Rhyd-yr-helig, 

 Lantwit Fardre, and Bettws, in the Llydfi VaUey. The section then passes 

 on through the Pennant rocks and coal-the steam and manufacturing coals, 

 and the ironstone beds-the lower shales and Rosser veins, FareweU rock, 

 carboniferous or mountain Umestone, to the old red sandstone, which may 

 be seen 2^ to 3 mUes north of Merthyr. 



Westwards of the Taff VaUey the measures thicken out considerably, and 

 eastwards from Merthyr they decrease in thickness. 



Mynydd-j- 



garreg, 

 Caermar- 



shire. 

 Yards. 



MerthjT. 

 Yards. 



Ebbw 

 Vale. 

 Yards. 



Llanell.v 



or 



Clydafh. 



Yards. 



— 900 



539 



180 



202 



243 



701 



133 



200 



80 



140 



From MynyddisUwyn coal to bottom 



vein coal 



From bottom vein to top of the lime- 



- stone 



Thickness of limestone to top of old 



red sandstone 



The old red sandstone, comprising the Breconshire Beacons 10 miles 

 north of Merthyr, Sir Roderick Murchison estimates to be 8,000 to 10 000 feet 

 thick; and he writes, "the grandest exhibitions of the old red san,itone in 

 ^ngland and Wales appear in the escarpments of the Black Mountain of 

 Herefordshire, and in those of the loftiest momitains of South Wales, the Fans 

 of Brecon and Caermarthen, the one 2860, the other 2590 feet above the sea In 

 no other tract of the worid which I have visited is there seen such a mass of 

 red rocks so clearly intercalated between the SUurian and the carboniferou.s 

 strata. 



By more recent observations the height of the Breconshire Fans above 

 mean tide level is 2,910 feet. 



The highest ground in the coal iield is the Gamfa<:h, a little south-west of 

 Hirwaun, 1,971 feet above sea-level, as shown on the recent ordnance maps. 



