eriod. But the great mass of the volcanic
rocks are much more recent, and may be confidently referred to the late
Cretaceous or early Tertiary epochs. Their resemblance to the great
trappean series of Western India, even in minute particulars, is
referred to by Mr. Blanford, who suggests the view that they belong to
one and the same great series of lava-flows extruded over the surface of
this part of the globe. This view is inherently probable. They consist
of basalts and dolerites, generally amygdaloidal, with nodules of agate
and zeolite, and are frequently coated with green-earth (chlorite). Beds
of volcanic ash or breccia also frequently occur, and often contain
augite crystals. At Senafe, hills of trachyte passing into claystone and
basalt were observed by Mr. Blanford, but it is not clear what are their
relations to the plateau-basaltic sheets.[2]

(2) _Magdala Volcanic Series._--This is a more recent group of volcanic
lavas, chiefly distinguished from the lower, or Ashangi, group, by the
occurrence of thick beds of trachyte, usually more or less crystalline,
and containing beautiful crystals of sanidine. The beds of trachyte
break off in precipitous scarps, and being of great thickness and
perfectly horizontal, are unusually conspicuous. Mr. Blanford says, with
regard to this group, that there is a remarkable resemblance in its
physical aspect to the scenery of the Deccan and the higher valleys of
the Western Ghats of India, but the peculiarities of the landscape are
exaggerated in Abyssinia. Many of the trachytic beds are brecciated and
highly columnar; sedimentary beds are also interstratified with those of
volcanic origin. The Magdala group is unconformable to that of Ashangi
in some places. A still more recent group of volcanic rocks appears to
occur in the neighbourhood of Senafe, consisting of amorphous masses of
trachyte, often so fine-grained and compact as to pass into claystone
and to resemble sandstone. At Akub Teriki the rocks appear to be in the
immediate vicinity of an ancient vent of eruption.

From what has been said, it will be apparent that Abyssinia offers
volcanic phenomena of great interest for the observer. There is
considerable variety in the rock masses, in their mode of distribution,
and in the scenery which they produce. The extensive horizontal sheets
of lava are suggestive of fissure-eruption rather than of eruption
through volcanic craters; and although these may have once been in
ex