KYXASTON : VOLCANIC ROCKS OF THE CHEVIOT HILLS. 185 
The Granite. The central and more mountainous portion 
of the district consists entirely of granite. It is well 
seen on the slopes of the Cheviot Hill, Hedgehope Law, 
Dunmoor Hill, in the Harthope burn above Langlee- 
ford, and in most of the burn sections within the 
granite area. The rocks forming the more central part 
of the mass are coarse in texture, and have a greyish 
or sometimes pinkish appearance. Towards the margin 
the rock usually becomes finer-grained, and sometimes 
is of a dark grey colour and resembles a fine-grained 
diorite. The dioritic varieties are well seen in the 
neighbourhood of Linhope, and in the Linhope burn, 
a short distance above the shepherd's house. Fine- 
grained varieties also occasionally occur, as for instance 
in the crags on the N.W. side of Cheviot, which are 
more acid than the normal coarse granite. 
The typical Cheviot granite consists of quartz, orthoclase, 
plagioclase, biotite, and augite. It is one of the few 
British examples of an augite-granite, and shows affinities 
in this respect to the augite-syenites of Monzoni, in the 
Tyrol. Another characteristic feature of the rock is 
the marked tendency of the quartz and orthoclase to 
be intergrown so as to form micropegmatite, and this 
is so constant in the finer-grained varieties that they 
may aptly be termed granophyi-es. The dioritic varieties 
merely difier from the more acid types in containing 
a higher proportion of the ferromagnesian constituents. 
In some specimens of the normal type enstatite has 
been detected, in addition to augite. 
Although of the same general geological age, the granite is 
later than the Andesites, and has been intruded into 
them. The surrounding lavas have in consequence under- 
gone contact metamorphism, and a microscopic study of 
the rocks has shown that this extends to at least half 
a mile from the granite margin. Junction sections 
between the granite and the andesite may be seen at 
