1826.] Sir C. L. Gihecke's Account, t)C. 271 



Article VIII. 



Account of a Mineralogical Excursion to the Counties of Gahuay 

 and Mayo. By Sir Charles Lewis Giesecke.* (Communicated 

 by a Member of the R. D. S.) 



County of Galway. 



I LEFT Dublin on the 14th of August, in conformity to 

 the directions of the Royal Dublin Society, and proceeded to the 

 County of Galway. I made my first excursion to Marble Hill, 

 and went the following day towards Woodford, on the new road 

 towards the Shannon, constructed by Mr. Killaly. Part of this 

 country consists of diluvial land, in which I found immense 

 blocks of beautiful conglomerate, consisting of fragments of rose- 

 red quartz and hornstone, of a dark leek-green jasper, and large 

 blocks of mica slate. Near Woodford there is a very extensive 

 stratum of meadow iron ore, which was worked by English 

 miners about a century ago, and afforded very good cast-iron, 

 which was shipped on the river Shannon. The turf, which 

 6overs the stratum of the iron ore occurs in enormous abun- 

 dance ; it approaches to moor-coal, and is of the best quality. 



The day after my arrival in Galway I went on an excursion to 

 Cunnamara. The black limestone is visible every where along 

 the road to Oughterard, a small town five miles from Galway, 

 which is visited very much during the summer season by the 

 gentry from Galway and its neighbourhood, on account of its 

 salubrious spa. As soon as you leave Oughterard, the junction 

 of the granite with the limestone is visible. In the evening I 

 arrived at Ballinahinch, the residence of Thomas Martin, Esq. 

 who received me with his usual kindness. 



He accompanied me on the following day to wjiat is called 

 the green marble quarry, but which is rather a quarry of precious 

 serpentine, belonging \.o his estates. It is situated in a valley 

 extending from the northward to the west peak of Lettery, to 

 as far as the middle of the place called the Twelve Pins, a series 

 of very acuminated coherent mountains. I found following up 

 the river, or rather torrent, traces of this serpentine at a distance 

 of a mile from the quarry. The rivulet, which took a serpentine 

 direction, has disclosed to the eye extensive strata of most 

 beautiful granular marble, of a pearl white colour, mixed with 

 rose-red, yellowish-red, blood-red, and biuish-grey. It alter- 

 nates with greenstone. The large serpentine quarry, where Mr. 

 Martin keeps from 150 to 170 labourers employed in blasting, 

 cutting, and sawing the immense blocks, is of an extraordinary 

 extent^ and seems to be inexhaustible. The serpentine, similar 



• From the Appendix to the Report oi'thc rrotecilings of the Royal Dublin Society,' 

 M»rch2, lb26. o / /> 



