64(» REPORT— 1901. 



6. Some Irish Laccolithic Hills. By G. H. Kinahan, M.R.I.A. 



The author begins by pointing out that laccoliths are not usually classed 

 among the elevators of hills. Of late years Professors Gilbert and Cross, of the 

 U.S.A. Survey — although not the pioneers — have brought this prominently 

 forward. A short list of writers on the subject is given. The south-east of 

 Ireland — Wicklow, Wexford, and Waterford — is mentioned as the portion of the 

 country in which they are conspicuous. Most of those in Wicklow and Wexford 

 were carefully mapped and described. 



Gilbert's definition of a laccolith, copied from a letter, is given. It partially 

 diflfers from his original, as in this he points out that fragments torn from 

 the conduit-pipe are usually found in the laccolith. This statement was made in 

 a reply to a query of the writer, who in his description of the laccoliths 

 of South-east Ireland had specially mentioned them. 



A few very characteristic laccoliths are particularly mentioned, such as the 

 range of the Wicklow and Wexford granite hills, this line of upheavals being 

 explained by diagrams illustrating that the granite had come up in pipes through 

 the undermost Oldhamians (Archsean) and lifted up tiie superior then horizontal 

 Ordovicians ; so that now, as a general rule, the Ordovicians, not the Oldhamians, 

 are in contact with the granite. A few remarkable laccolithic hills in other 

 parts of Ireland are also mentioned. 



7, The Geological Distribution of Fishes in the Carboniferous Rocks of 

 Scotland. By Dr. R. H. Traquair, F.R.S. 



The Geological Distribution of Fishes in the Old Red Sandstone of 

 Scotland. By Dr.R. H. Traquair, i^.i^.-S. 



9. Perim Island and its Relations to the Area of the Red Sea. 

 By Catherine A. Raisin, D.Sc. 



This paper describes briefly rock specimens from Perim Island collected and 

 placed at the disposal of the authoress by Mr. J. A. Eupert Jones (sub- 

 lieutenant R.N.R.), now stationed at Aden. 



The island, as shown in the Admiralty chart, has somewhat of a horse-shoe 

 shape, enclosing a harbour opening to the south. Low plains, less than 12 feet 

 above sea-level, extend in from the coast, especially at the north, and consist of 

 raised beaches, but most of the southern and eastern parts are hilly, reaching 

 249 feet at the highest point. 



The specimens received are all from volcanic roclvs. The surface, according to 

 Mr. Rupert Jones, is composed mostly, to a depth of about 7 feet, of loose 

 blocks (i feet or less in diameter), often imbedded in calcareous sand or mud. The 

 underlying rock is exposed in cliffs and in quarries, and occurs generally in roughly 

 horizontal layers. One mass i7i situ (near Balfe Point) is a not very basic basalt 

 (almost an andesite") crowded with felspar microliths with marked fluidal orienta- 

 tion, and is probably a lava flow. Another reddish rock with scattered rounded 

 vesicles (from a cliff north-east of the harbour) approaches a microcrystallinc 

 basalt in character, aud consists of much plagioclase, clear gum-like augite, some 

 red brown ferruginous olivine or pyroxene, and a little black speckled glassy base. 

 In another spot (near Balfe Point) a whitish tuff or fine agglomerate is quarried, 

 and consists largely of fragments of pumice with some broken felspar, augite, and 

 other crystals. 



The surface blocks in one or two examples consist of fragmental rocks. One 

 is a red more basic tuff, containing thin black streaks, apparently of a spherulitic 

 glass. The blocks, however, are mostly scoriaceous and vesicular, petrologically 



