Gatway Excursion. — Geology. 237 



^he marble quarries at Menlough were also visited, where an excellent 

 jet-black marble is obtained, ornamented with white s^zWows oi Producttis 

 and corals. It seems a pity that this marble and the serpentine are not 

 more fully worked, as facilities for transport are all that can be desired. 



On the shores of the lake near Clare-Galway Abbey the limestone is 

 curiously bored by holes, varying from half to one-and-a-half inches in 

 diameter, and sometimes extending downwards for six or eight inches. ' 

 Their origin is as yet uncertain, the alternative suggestions being either 

 the action of carbonic acid from vegetation, etc., or the burrowing of 

 land snails or of marine animals such as Pholas. Travellers on the line 

 to Clifden will see, on the right hand side, soon after leaving Galway, 

 some of the curious " mushroom" rocks, produced by softer inferior layers 

 weathering away more rapidly than harder superior layers. 



The glacial geology of the district is very interesting, the hard, white 

 quartzite of the Bens being splendidly glaciated ; and capital ice-worn 

 surfaces were seen close to Recess station, and also on the way to Ben 

 Lettery, the rock being finely smoothed and polished, with deep ice- 

 groovings. The drift sections at Gentian Hill yielded many erratics. 

 The grey clay is excessively hard and compact, forming a cliff a quarter 

 of a mile long and about thirty feet high, with large and small erratics 

 projecting from the surface, the retentiveness of the matrix being evi* 

 denced by the great masses that stand out in all directions ; similar sec- 

 tions occur on islands and on the coast about this locality. Many 

 boulders are of black Carboniferous limestone with bands of white Pro- 

 ductus about three inches deep, the whole surface being exquisitely 

 polished and striated, others are Connemara granites, including the 

 typical Galway variety, remarkable for the scarcity of mica, and the 

 handsome crystals of pink orthoclase felspar, recalling the famous Shap 

 granite ; specimens of serpentine also occur as erratics. 



On the Aran Islands, in Galway Bay, many of these rocks occur as 

 erratics. Also there are found specimens of a fine-grained red quartzite 

 said not to occur now anywhere in situ. It would be impossible to con- 

 clude without a reference to the remarkable cliflf-scenery of these 

 islands, where the slightly-dipping limestones have been undercut by the 

 sea into mighty shelves, over which the Atlantic waves play ceaselessly, 

 whilst upper terraces are tenanted by myriads of sea-birds, and the top 

 of the cliffs between 50 and 100 feet above the sea are swept bare at the 

 edges, huge piles of stones forming a rampart many yards inland, de- 

 monstrating what the force of the surges must be, when their spray can 

 do such mighty work. Here and there, in the face of these grand cliffs, 

 a bed of shale gives rise to a water-spring, falling in delicate veils of 

 spray into the ocean, an exquisite rainbow perpetually spanning the 

 abyss. The causes that result in such beautiful effects are full of geo- 

 logical interest, and the whole excursion was replete with such oppor« 

 tunitiee for the geologists o| the party. 



