71 



THE GEOLOGY OF HOOK POINT. 

 By Professor E. Harkness, F.R.S. F.G.S. 



(Continued from page Z2.) 



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 from Hook the carboniferous slate increases in thickness, until we 

 find it in the county of Cork, separating the sandstone strata below from 

 the lower portion of the carboniferous limestone above, by an interval, 

 in some instances, reaching 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 

 inferior 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 



