Cote—The Rhyolites of the County of Antrim; with a Note on Bauzite. 79 
containing pebbles of rhyolite, found at Ballypalady and at the Libbert Mine, 
Glenarm,* are probably derived from hidden masses lying to the east of our line; 
and Mr. M‘Henry states that he has observed similar beds at other placest in the 
county of Antrim. 
J 1.—TEMPLEPATRICK. 
A large mass of rhyolite, of a whitish to a pale pink-brown colour, is seen in 
a fine section formed by the north side of Templepatrick quarry. It lies above 
the chalk, from which it is separated in most places by an irregular zone of 
reddened flint-gravel and dark clays. The rock has a distinct and uniform fluidal 
structure, and breaks parallel to this, like many Icelandic examples. It contains 
small porphyritic grains of quartz, which are far more sparsely scattered than 
at T'ardree, a few transparent felspars, and here and there a hexagonal plate 
of biotite. In contact with the gravel or the chalk, it has decomposed to a soft 
greenish clay, the weathering away of which has produced a horizontal groove 
along the quarry-face. This extreme alteration of what was probably at one time 
the most glassy portion of the rock is an unusual feature, and must be explained 
by the ease with which water can attack the material at its surfaces through the 
surrounding permeable strata. Something akin to this decomposition is seen in the 
glass of a rhyolitic andesite from Tay Bridge End, described by Professor Judd, 
which retains its essential structures, and yet falls into powder when placed in 
cold water. 
The rhyolite of Templepatrick has been traced by the officers of the Geo- 
logical Survey to the south of the railway, and also to the west, across the church- 
yard. My own specimens, freshly dug up in the latter spot, differ considerably 
from the more boldly developed masses in the chalk-quarry. There are no con- 
spicuous porphyritic crystals, and the fluidal structure is faint and irregular. 
Numerous small angular lumps of rhyolite are embedded in the mass. The 
specific gravity of this rock is 2°44. 
A delicate shimmer appears on some of the joint-surfaces of specimens from 
the churchyard, and suggests the formation of silky zeolites. Under the micro- 
scope, the groundmass is seen to be exceedingly fine-grained, with abundant 
aggregations of globular crystallites, the ‘‘cumulites” of Vogelsang. One or 
two minute and colourless radial spherulites occur, and the whole seems but little 
* Sir A. Geikie, ‘‘Anniversary Address,’ Quart. Journ. Geol. Soc. London, vol. xlviii. (1892), 
Proceedings, p. 168. Also A. M‘Henry, op. cit. p. 262. 
t Op. ctt., p. 268. 
{ “Volcanic Rocks of the North-east of Fife,” Quart. Journ. Geol. Soc. London, vol. xlii. (1886), 
p- 431. 
N2 
