290 Scientific Proceedings, Royal Dublin Society. 



To the north-east, forming a hilly country south-west of Carling- 

 ford Lough, are peculiar Granitic and other Intrusive rocks. 



In different places in the Ordovicians, veins of lead and copper 

 have been found, and at Jonesborough antimony; while mines 

 were worked about the year 1840 at Salterstown, and near Clogher 

 At the junctions of the Grranyte and the Ordovicians traces of lead, 

 occur in different places. 



Near Clogher Head there is a poor iron- ore, and in different 

 places in the hills are the ruins of old iron works : the ore for the 

 latter may have been imported. 



Mayo. 



In this county about half the area is occupied by Metamorphic 

 rocks (probably Ordovicians and Cambrians) and their associated 

 Granytes. Some of the Metamorphic rocks are said to be Lau- 

 rentians, but lithologically, and apparently petrologically, the 

 younger rocks of the series are similar to the Co. Gralway rocks 

 that carry fossils of Llandeilo types. On them, to the south- 

 west, and extending into the Co. Gralway, are Silurians; while 

 smaller tracts of the same age occur south, west, north, and north- 

 east of Clew Bay, the last in Croagh Moyle, being the largest. 

 The rest of the area is occupied by Carboniferous rocks, Coal 

 Measures, &c. 



A valueless coal occurs in the Coal Measure, but associated, 

 with it is clay-iron-stone, that was worked to be smelted in 

 Gildeas' furnace at Port Eoyal. 



Limonite, or hematite, was mined in Cross and Tallaghan, 

 barony of Erris, and in the Cloonaghan and Deel river valleys, 

 barony of Tirawley. Formerly Sir Greorge Shaen smelted and 

 milled iron near the Mullet ; while a little later Kutledge had 

 works on the Deel. Both these Iron Masters had to discontinue 

 their works for want of fuel when the woods were exhausted. 



At Port Eoyal, near Ballinrobe, the Grildeas, in Charles II. 's 

 time, were given a grant of land, in which they mined and 

 smelted iron. The ore principally used was bog-iron-ore, mixed 

 with the clay-iron-stone raised near Balla, some miles to the 

 north ; while tradition has it that they also procured limonite 



