212 Scientific Proceedings, Royal Dublin Society. 
cross from the south to the north side thereof; and lately I have 
learned from Mr. Kinahan’s work that they are most irregular, 
occurring in isolated masses more or less surrounded by killas, 
they being situated in general to the south of the mineral channel, 
but not always; as tothe East they are found northward of the 
main lode. Mr. Kinahan has also proved that, although some of 
the felspathic rocks are intrusive felstones, the majority (the 
hornstones and quartz rocks of Weaver) are metamorphic rocks ; 
the felspathic tufts, the slates and shales, in places having been 
altered into rocks like hornstone, felstone, and other igneous rocks. 
The felspathic rocks (felstones and hornstones) are most im- 
portant, as a careful mapping of them has proved the existence of 
great disturbances in the country older than the formaticn of 
the mineral veins ; other breaks seem to have been produced con- 
temporaneously with the vein fissures, and some are evidently 
newer, as has been proved by the subterranean operations.* 
We may expect further details of the geology of the district 
when the examination of it is complete, and the new maps and 
report of the officers of the Survey are published. 
General Description of the Mineral Lodes. 
The lodes upon which mining operations have been carried on 
east of the Ovoca occur, as previously stated, principally in killas 
(slates and shales), in a length of country extending from the 
Ovoca river for about six miles in the direction of N.50° E+ The 
lodes are not, however, continuous for this distance, as they are 
broken and displaced by numerous faults, and in places interven- 
ing tracts of “ Dead Ground ” occur, in which the regular lodes 
have not been found. The ground will be described beginning to 
the west. 
Tigroney and West Cronebane. 
In the Ovoca valley there is a large and very well-displayed 
fault, known as the Great Flucan, which, together with the east 
head in Ballygahan Mine to the west, causes a left-hand displace- 
* Mr. Kinahan’s work I more especially mention, as I have had the advantage of ac- 
companying him on numerous occasions during his examinations of the districts, and am 
consequently more or less familiar with his conclusions. 
+ All bearings are magnetic, 22°5 W. of true, 
