KYNASTON : VOLCANIC ROCKS OF THE CHEVIOT HILLS. 187 
often stand out in bold relief when occurring amongst 
them. They are common throughout the entire area of 
the Cheviots, and frequent examples may be seen in 
the river Breamish, in the Common burn, and in the 
Carey burn. 
The quartz-felsites are not so common as the porphy rites, 
and usually occur in, or in the neighbourhood of, the 
granite. Several examples of the normal type may be 
seen in the river Breamish, above Linhope ; while a 
beautiful examplo of a biotite-quartz-felsite, showing 
relationships to some of the porphyrites, may be seen 
in the river Coquet, a quarter of a mile above Shill- 
moor, and again in the Ridlees burn, east of Quickening 
Coat. (For description see Teall, Geol. Mag., 1885, 
p. 107, and "British Petrography," p. 343.) 
Besides quartz-felsites we also find granophyres and micro- 
granites cutting the granite, and these rocks shade into 
one another through intermediate varieties. In fact, by 
collecting a large number of specimens from the dykes 
of this area, it is possible to show intermediate varieties 
between the quartz-felsites and the porphyrites, so that 
it is extremely probable that the rocks have a common 
origin. 
To glance briefly at the sequence of events which have 
marked the volcanic history of the Cheviots. The first 
period of volcanic activity was evidently marked by the 
eruption of immense quantities of andesitic lava. This, 
which we may call the extrusive phase, was followed, as 
is proved by the phenomena of the granite and the dykes, 
by the intrusion of material partly of intermediate and 
partly of acid composition. This intrusive phase com- 
menced with the intrusion of the augite-granite into the 
contemporaneous lavas. The intrusion of the dykes and 
sills followed the consolidation of the granite, and con- 
stituted the latest phase of the volcanic activity of the 
district of which we have any record. Petrological 
