62 CAMBRIAN. 



The lower beds may be studied on the range between the Eden 

 and Mawddach, and near Dohiaelynllyn. The upper beds are ex- 

 posed near Dolgoed, Hafod-fraith, and Llanelltyd. The beds are 

 also to be seen at St. Davids and Solva in South Wales. 



The slates are sometimes worked for economic purposes, as at 

 Caen-y-coed, and Llanelltyd, but they are not of much commercial 

 importance. The gold-mines of Hafod-y-morfa, Cefn-deuddwr, 

 have been opened in these beds. Cwm-eisen gold-mine is in hard 

 flags of this group and Menevian beds — the metal occurs in a 

 quartz vein, which is much disturbed. The Rev. W. S. Symonds 

 observes, " From what I know of these gold-mines, I have no faith 

 in Welsh gold, inasmuch as the precious metal occurs only on the 

 surface, and dies out when followed into the heart of the rock." 

 He notes the proximity of igneous rocks. ^ Ores of copper, lead, 

 and zinc occur in small quantities. 



Ffestiniog Beds, 



Mr. Belt proposed (1867) to restrict the name of Ffestiniog 

 group (of Sedgwick) to the hard sandy and micaceous flags 

 containing Lingulella Davisii, and Hymenocaris vermicauda, which 

 lie conformably upon the Maentwrog beds. The group is about 

 2000 feet in thickness. 



Two divisions have been made in this group •} — 



tjo r ( Tough bluish-grey flags, with LingiileHa Davisii (small variety), 



■? •/ I Upper, \ Hymenocaris ver»ueauJa, Bellerophon Cat/ibriensis, Olemts 



S'^X ( micruncs. 5° f*^*^'- 



(J P-5 I ;-.,,/ Brown, grey, and yellow flags, with Lingtilella Davisii, H. ver- 



P^ V oiut? . y micauda, Cricziana, Buthoirephis (SlVmcms). 2000 feet. 



The beds occur in the neighbourhood of Maentwrog and Dolgelly. 

 The river ]Mawddach cuts through the whole of the beds between 

 Rhiwfelyn and Hafod-fraith. They cross the Wnion near Glyn 

 IMaldon, and then by Gwern-y-barcud and Tyn-y-craig, range to 

 Coed-y-garth, and into the estuary of the Mawddach. They occur 

 at Ramsey Island, near St. Davids. The lower beds occur near 

 Penmaen-pool, Mynydd-gader, and on Moel Hafod-Owen. At 

 the last-named locality Mr. John Plant has obtained many fossils.' 

 The upper beds may be studied at Gwern-y-barcud. 



The Hollybush Sandstone of Malvern is placed on the horizon of 

 the Ffestiniog beds. 



Good building-stones and flags are worked in the Ffestiniog 

 Beds ; and copper-ore has been obtained at Glasdir. Mr. Belt says 

 the numerous quartz veins intersecting the beds near Dol-y- 

 frwynog all contain a little gold, but have nowhere on this horizon 

 been worked with profit. 



1 Records of the Rocks, p. 67. 



2 G. Mag. 1867, p. 540. 



3 Q. J. xxii. 505. 



