1826.] Excursion to the Counties ofGaltoai/ and Mayo. 273 



ruins of a monastery. I proceeded by the Neal and Ballinrobe 

 toWestport, where I arrived the same evening. The rocks all 

 along the road consist of greyish-black compact limestone, 

 interspersed with spots and veins of white calcareous spar. 



The following morning 1 went to a lead mine called Sheffiy, 

 twelve miles to the south-west of Westport, which is worked at 

 present by the Hibernian Mining Company, and is on the estate 

 of the Marquis of Sligo. The mountains consist of smoke-grey 

 and greenish-grey clay slate, alternating with chloriteslate very 

 much decomposed on its surface, and intersected by veins of 

 yellowish-white common quartz of ditierent breadths. The vein 

 of lead ore, which runs in a south-westerly direction, is opened 

 at a distance of about 400 paces from the new road constructed 

 by Mr. Bald, where has been driven a level of about twenty- 

 seven fathoms. The lead ore (common coarse granular galena) 

 runs through the clay slate, which is of an ash-grey colour, and 

 somewhat decomposed. It occurs partly massive, partly crystal- 

 lized in cubes, and is accompanied by copper pyrites, partly mas- 

 sive, partly crystallized in rhomboids and three-sided pyramids, 

 sometimes pavonized. The other minerals, which are found in the 

 vein along with the ore, are common white quartz, massive, and 

 crystallized in six-sided prisms, brownspar of a yellowish-white 

 colour, prase, yellow iron ochre, barytes, and a yellowish-green, 

 earthy substance. There are scattered about in the diluvial 

 land fragments of leek green flint, hornstone, and common 

 quartz. I went along the road through the chain of mountains, 

 which consists of clay slate, to the fishing lodge of the Marquis 

 of Sligo down to Killery bay, which separates the Counties of 

 Galvvay and Mayo. 



The rock that borders the coast of the county of Mayo in 

 Killery Bay is hornstone porphyry, of a liver-brown colour, with 

 small white and reddish-white crystals of felspar, and veins of 

 green talc. It is covered in some places by a coarse quartz- 

 conglomerate. I was informed that not far from the village 

 Bonduragh there was an iron mine worked about thirty years 

 ago. 



On one of the following days I made an excursion to the Reek 

 and Croagh Patrick, an extensive mass of rocks, which consist of 

 mica slate, with overlying common serpentine. In the latter 

 there is imbedded common leek-green talc, and greyish-green 

 amianthus. 



Achill Island. 



I proceeded in a boat belonging to the Marquis of Sligo, 

 who very kindly assisted me in my excursion, ucioss Clew Bay 

 to Achill Island, twenty miles from Westport. The vast moun- 

 tain tracts of this island consist of mica slate of a very fine slaty 

 texture, witli beds of the rock, called by the late Werner white- 

 New; Ser/«, VOL. XI. T 



