71 
THE GEOLOGY OF HOOK POINT. 
By Professor R. Harkness, F.R.S. F.G.S. 
(Continued from page 32.) 
The paleontology or the study of the fossils of Hook Head is, if it 
be possible, even more interesting than its physical geology. As soon 
as ever we cross over the sandstones, and ascend into the higher strata 
of the Carboniferous series proper, we reach a domain abounding with 
animal life. Almost immediately above the sandstones which afford the 
remains of the fossil plants, we reach a zone having a distinct mineral 
character. This zone consists of a black shale, a substance which was 
originally black mud deposited by the sea, and this black shale is an 
important member of the great Carboniferous series of the south of 
Ireland. At Hook, it is a very degraded form of that member of the 
Irish carboniferous series known under the name of " carboniferous 
slate." In this locality it has a thickness of only a few yards, but west- 
ward fi'om Hook the carboniferous slate increases in thickness, until we 
find it in the county of Cork, separating the sandstone strata below from 
the lower poi'tion of the carboniferous limestone above, by an interval, 
in some instances, I'eaching to about 4,000 feet. At Hook, this ancient 
muddy sea-bottom seems to have existed for a shorter time than 
towards the westward, and was succeeded by a sea containing a con- 
siderable portion of lime in its waters. 
The limestone which succeeds the black shale at Hook is not of so 
pure a character as that which forms the general great mass of the 
Lower Limestone of Ireland. It is largely impregnated with mud, and 
seems to have resulted from nearly the same physical conditions as the 
iufei'ior black shale, differing only from the latter in containing a 
greater amount of lime. The black shale and the limestone equally 
afford fossils, and they show us to what an extent animal life abounded 
in the seas during this early geological period. All geologists con- 
versant with Carboniferous fossils are not only aware to what an ex- 
tent many of the forms of life of this period abound in this locality, 
but likewise know the perfection of the Hook organisms. Among 
zoophytes — those plant-like animals which, in external form, nearly 
