Sortas—On the Variolite and Associated Igneous Rocks. 95 
one on the variolite of Cerriggwladys, where it was discovered by 
Professor Blake, and this closely resembles that which we are 
about to describe; and another on a Tertiary example from 
Annalong, county Down.! I am glad to be able to add to the 
list a second Irish variolite possessing the essential characters. 
of the variolite of the Durance. It occurs at Tougher or Round- 
wood, near Dublin, where I found it while on an expedition with 
Professor Cole. 
The variolite of Roundwood forms part of an igneous complex,. 
which includes diabase, spilite, and consolidated volcanic tuff. 
The complex is exposed in a series of isolated hummocks, rising 
from peaty and marshy ground on each side of the road from 
Roundwood to Annamoe and Glendalough. The first hummock is 
met with half-a-mile south of the Roman Catholic chapel of 
Roundwood, and the series extends a little over half-a-mile in a 
more or less southerly direction, with a breadth of about 300 
yards. Although not represented on the published map of the 
Geological Survey, this interesting patch of igneous rocks was 
evidently not unknown to the surveyor. So long ago as 1848 
Professor Oldham’ called attention to it ‘‘as a small boss of 
Serpentine,” for which rock the strikingly green diabase might 
without microscopical analysis be very well mistaken. Mr. 
Kinahan subsequently alluded to it as ophite, and with the typical 
ophite of the Pyrenees it has as much in common as any ophitic 
diabase necessarily must ; but beyond a general resemblance there 
seems to be no sufficient justification for the name. Specimens of 
the diabase had evidently come under the observation of Jukes,’ 
who with the true petrographical instinct which distinguished him 
was contented to name them greenstone. It appears further that 
it is only by some oversight that this area does not appear on the 
published map. Mr. Watts has kindly allowed me to inspect the 
6-inch map on which the surveyor’s work is recorded, and there it 
is plotted carefully enough, -with the remark that it should be 
1 «The Variolite of Annalong,’’ Co. Down, Sci. Proc. Roy. Dublin Soe. (N.S.), vol. 
vii. p. 115 (1892). 
2 Oldham, ‘‘ Notice of the Occurrence of a Small Boss of Serpentine in the County 
Wicklow,’’ Journ. Geol. Soc. Dublin, vol. iv., p. 202. 
3 Jukes, Catalogue of the Collection of the Geological Survey of Ireland, p. 14. 
