144 Scientific Proceedings, Royal Dublin Society. 



of the fire-clay having been used elsewhere, except very locally 

 for the lining of hearths. 



A steatitic clay, the " hack," or weathered portion of the beds 

 of pure phyllite and intrudes of steatite, is also used for hearths 

 and the lining of forges (vol. v., p. 254). 



An unctuous clay, called Doab in Connaught, occurs in places 

 in the granitic and metamorphic areas of Gralway, Mayo, Donegal, 

 &c. It is very commonly used for making floors and for mortar ; 

 while from some of the purer varieties whitewash can be made. 



Porcelain, or China-clay , or Kaolin. — A clay due to the decomposi- 

 tion of very felspathic rocks ; it may occur as a surface accumula- 

 tion, or as the weathered portion of a felspathic dyke or intrude, 

 or it may be artificially made. Baron von Richthofen has proved 

 that Kaolin is manufactured by the Chinese from petrosilex or 

 granulite ; its name was derived from " Kaolin," anglice, " Low 

 ridge," the name of the hill on which the China-clay was originally 

 manufactured. The name is now applied promiscuously to the 

 artificial and natural clays. 



At Kilranelagh, near Baltinglass, Co. Wicklow, kaolin of a fine 

 quality has been obtained ; at Tullow, Co. Carlo w, there is a 

 porcelain clay, but partially impregnated with iron ; while a little 

 S. E. of Westport, Co. Mayo, a decomposed petrosilex forms a 

 dyke of kaolin. Lewis mentions " clay fit for porcelain and 

 every other description of earthenware " as having been sent from 

 Mayo to England, but he does not mention the locality where it 

 was procured. The Ballymanus dyke, Co. Wicklow, is a silicious 

 kaolin. In different places there are felspathic rocks suitable 

 for the manufacture of porcelain clay. Near the sea, in the 

 country south-westward of Eoundstone, Co. Galway, there are 

 dykes of very pure felsite, suitable for kaolin manufacture, 

 while in the same county, near the city and in other places in 

 the vicinity of Gralway Bay, are very pure leptinites and other 

 felspatic rocks. At Belleek, Co. Donegal, kaolin is manufactured 

 from a pink orthoclase ; this is kept for the finer ware {Belleek 

 ware), while the clay for the delf and common wares is made from 

 imported stone. 



In the Co. Wicklow, in the vicinity of the Ovoca mines, and in 

 other places, there are very pure felsites and leptinites. Attention 

 was directed to these years ago by Weaver ; but as yet they have 



