106 Cotn—The Rhyolites of the County of Antrim; with a Note on Bauxite. 
together with the white clayey products at Templepatrick, suggests that the 
rhyolites of Co. Antrim may have had some share in the origin of bauxite. 
The famous deposits of les Baux, Bouches-du-Rhéne, do not seem to have 
been traced to any igneous source. They are interstratified with Lower 
Cretaceous beds, and also with limestones of the Danian stage, and were regarded 
by M. H. Coquand* as formed by the deposits of mineral springs opening into 
lakes. They are often of a strong red-brown colour, and are sometimes as 
pisolitic as the lake-iron-ore which is associated with them. Of course, the 
aluminium hydrates, none the less, may have been brought down in the form of 
fine mud by rivers, which flowed over some igneous area. But the bauxites of the 
county of Antrim are more comparable in their mode of occurrence to those of the 
Vogelsgebirge in Germany, which are distinctly associated with volcanic débris. 
Near Giessen, the weathering of a basalt has produced a bauxite with only 4°6 to 
10 per cent. of silica, and about 50 per cent. of alumina. The minerals of 
the original basalt, and the structure of the rock, are still distinctly recognis- 
able.t Further south, near Hanau, a basalt has been described by Petersent as 
giving rise to a bauxite and a bauxitic clay; these products similarly retain 
structures and crystals that prove their igneous origin. 
Mr. G. H. Kinahan§ has suggested the derivation of the bauxitic clays of 
the county of Antrim from lithomarge bleached by the action of peat above it; but 
this does not explain how the aluminium silicates of what is known as lithomarge 
could become converted into aluminium hydrates. The association of bauxite in 
Ireland with pisolitic iron-ore suggests that various decomposition-products of 
basalt have accumulated successively in lakes. This may be true of the Ballintoy 
area||; but the section at the Libbert Mine, Glenarm, points to the underlying 
rhyolitic conglomerate as directly connected with the bauxite. A specimen of 
this conglomerate is in the collections of the Royal College of Science for Ireland, 
and Mr. M‘Henry has kindly given me, for comparison, a sample of the Glenarm 
bauxite. The pebbles and felspathic ground in the former rock have decomposed 
to a white sectile clay, similar, except in colour, to the product at Scolboa. The 
specific gravity of the white ground, determined in methylene iodide, is 2°44, 
that of the bauxite of Glenarm being about 2°42. The bauxite of Wochein in 
* «Sur les Bauxites de la chaine des Alpines (Bouche du Rhone) et leur age géologique,” Bull. 
Soc. géol. de France, 2me. sér., tome xxviii. (1871), p. 111. 
+ Will and Lang, quoted by Roth, ‘‘ Allgemeine u. chem. Geologie,” Band ii. (1885), p. 341. 
{ ‘Uber den Anamesit von Riidigheim und dessen bauxitische Zersetzungsproducte,” Abstract in 
Neues Jahrb. fiir Min., &c., 1894, Bd. i., p. 460. 
§ «Notes on some of the Irish crystalline Iron Ores,” Journ. Roy. Geol. Soc. Ireland, vol. vi. 
(1886), p. 307. 
|| Mem. to Sheets 7 and 8, Geol. Surv. Ireland, p. 24. 
4] M‘Henry, ‘‘ Age of the Trachytic Rocks of Antrim,’ Geol. Mag., 1895, p. 263. 
