ey might belong
to any age between the beginning and the end of the warmer Eocene
period; and that they cannot be of earlier, and are unlikely to be of
later, date."--_Trans. Palaeont. Soc._, vol. xxxvii. (1883).

[2] Having dealt with this district rather fully in _The Physical
Geology and Geography of Ireland_ (Edit. 1891, p. 81), and also in my
Presidential Address (Section C.) at the meeting of the British
Association, 1874, a brief review of the subject will be sufficient
here, the reader being referred to the former treatises for fuller
details. The following should also be consulted: Gen. Portlock, _Geology
of Londonderry and Tyrone_ (1843); Sir A. Geikie, "History of Volcanic
Action during the Tertiary Period in the British Isles," _Trans. Roy.
Soc. Edinburgh_, 1888; and the _Descriptive Memoirs_ of the Geological
Survey relating to this tract of country.

[3] Owing to the superposition of the basaltic masses on beds of chalk
throughout a long line of coast, we are presented with the curious
spectacle of the whitest rocks in nature overlain by the blackest, as
may be seen in the cliffs at Larne, Glenarm, Kinbane and Portrush. (See
Fig. 27.)

CHAPTER II.

SUCCESSION OF VOLCANIC ERUPTIONS.

(_c._) _First Stage._--The earliest eruptions of lava in the North-east
of Ireland belonged to the highly acid varieties, consisting of
quartz-trachyte with tridymite.[1] This rock rises to the surface at
Tardree and Brown Dod hills and Templepatrick. It consists of a
light-greyish felsitic paste enclosing grains of smoke-quartz, crystals
of sanidine, plagioclase and biotite, with a little magnetite and
apatite. It is a rock of peculiar interest from the fact that it is
almost unique in the British Islands, and has its petrological
counterpart rather amongst the volcanic hills of the Siebengebirge than
elsewhere. It is generally consolidated with the columnar structure.

[Illustration: Fig. 29.--Part of the section shown in the quarry at
Templepatrick, showing the superposition of the basalt (_d_) to the
trachyte (_b_), with the intervening bed of flint gravel (_c_). All
these rocks are seen to rest upon an eroded surface of the Chalk
formation (_a_).]

The trachyte appears to have been extruded from one or more vents in a
viscous condition, the principal vent being probably situated under
Tardree mountain, where the rock occurs in greatest mass, and it
probably arose as a dome-shaped mass, with a somewhat exte