WATSON — THE HEMATITE DEPOSITS OF GLAMORGANSHIRE. 



253 



unproductive region relates only to the troughs or positions near to 

 the synclinal axes, and to which the exoteric agents, which aided 

 mainly in the deposition of the ironstone, could never possibly have 

 penetrated. 



On the statement of this fact, that these veins of haematite may be 

 considered superficial, the question of origin next arises. And here is 

 immediately opened to us the wide inquiry of the relationship of 

 mineral veins to the rocks which inclose them. With veins filled 

 with other ores than those of iron, the origin of the metallic accu- 

 mulations may, in most cases, be refen-ed to causes acting from 

 distant centres in the interior, assisted by those subterranean changes 

 which are the universal result of the calorific and electrical agents 

 that are always at work in the earth's crust. 



In a few words, the origin of these veins may be considered esoteric, 

 or produced from within. AVith iron, however, in nearly all cases, 

 an external derivation must be sought. The great solubility of its 

 salts and chemical combinations, their affinity, and the proneness of 

 the metal itself to enter into union with substances with which it may 

 have newly come in contact, gives to iron in its various forms a' more 

 world-wide distribution than is perhaps possessed by any other 

 metallic mineral. Its local accumulation will therefore probably be 

 the result of its chemical segregation and the nature of its combina- 

 tions ; in other words, the particular class of ore will be governed 

 by the mineral character of the transported matter, those portions 

 which do not separate as ore solidifying into the vein-stones, or 

 "gangue," which may either be amorphous or crystallized, according 

 to circumstances. 



In the Llanharry district there is a bed of hsematite five feet in 

 thickness, of the same mineralogical character as the Llantrissant 

 deposit, and occupying a similar geological position in the limestone. 

 This bed has been anciently worked to some extent at Lleche, and, 

 from the form of the chambers, or " stalls," and the narrow pit by 

 which access was gained to the vein, probably by the Komans, 

 who certainly were acquainted with the existence of the ore in the 

 district. Some coarse red pottery, of undoubted Eoman manufac- 

 ture, was found a few years since buried in a small pit made in 

 the bottom of an ancient stall-working at Ty-Ischaf. The pottery, 



VOL. IT. u 



