aed 
1869. | TATE AND HOLDEN—ZRON-ORES WITH BASALTS. 155 
to its position relatively to that of the underlying White Limestone 
—which, by the way, is of varying thickness, and that often within 
very limited distances. At Red Bay the iron-ore is about 200 feet 
above the upper line of the White Limestone, whilst at Galboly, two 
miles to the east, in the direction in which the White Limestone 
thickens, it is about 300 feet vertically above that formation. 
ITI. Ortern or tHE Pisorriic [Ron-orez. 
1. Suggested Theories—Four theories may be suggested to account 
for the origin of the iron-ore; these are :— 
(1) Sedimentary theory, which implies a derivative origin, but 
is at variance with the petrological features—the distribution of the 
mineral particles has evidently been regulated by some other force 
than that of gravity. Mr. Du Noyer, in a paper on the Geology 
of Island Magee, read before the Natural-History and Philo- 
sophical Society of Belfast, November 25, 1868, endeavoured to 
demonstrate that the iron-ore in the basalt of Island Magee was 
entirely due to the action of water, “that it was as true an aqueous 
conglomerate as if it had been found in the heart of the Old Red 
Sandstone.” From this opinion we most emphatically dissent, 
though at the same time we fully concur with him when he assigns 
such an origin to the iron beds at Ballypalidy. 
(2) Theory of Deposition, implying either a precipitation of the 
ferruginous material from chemical solution, or segregation by or- 
ganic agency. We believe that the state of combination of the 
oxides of iron, the intimate structure of the spheroids, and the 
petrology necessitate some other explanation. 
(3) Igneous theory, implying production by direct volcanic action. 
Though specular iron is enumerated among the minerals emitted 
from active voleanoes, and magnetite and iron pyrites are accessory 
constituents of several of the basaltic strata, yet such an origin does 
not meet the requirements of the case in point. The distribution of 
the spheroids of pisolitic ore demands either a shower of the ferrous 
nodules over a large area, the smaller ones falling before the larger, 
or a flow of volcanic mud with suspended spheroids, the smaller 
sinking first in the mass—both assumptions being highly im- 
probable. ; 
(4) Metamorphic theory.—It is only by metamorphism that all 
the phenomena connected with the pisolitic ore can be interpreted. 
By metamorphism we understand something more than the effects 
of heat, and employ the term in its widest significance. We will 
now proceed to point out what appear to have been the several 
stages of metamorphic action by which the pisolitic ore has been 
elaborated out of basalt. 
2. Origin of Bole and Inthomarge.—There can be no doubt that 
the lithomarge and bole alternating with compact basalts are but 
decomposed basalts. The passage from basalt to lithomarge and 
bole can be traced in all cases; not unfrequently large masses of 
basalt are to be seen in the midst of the lithomarge, the concentric 
layers presenting all the varieties of texture and colour between 
