236 
THE SILURIAN VOLCANOES 
BOOK IV 
base of the volcanic group. The view of the more eastern hill, as seen 
from the west, is at once suggestive of a “ neck.” These masses measure 
roughly about a square mile each. 
With the acid intrusions may possibly be associated some of the other 
masses ol granophyre, microgranite and granite (felsite, felstone, quartz-felsite, 
syenitic granite, quartz -syenite, elvanite), which have long attracted 
attention in this region. The largest of these intrusions is the tract of 
granite which stretches from Eskdale down to near the sea -coast as a 
belt about ele^'eu miles long and from one to three miles broad. Another 
large mass is the granophyre or “ syenite ” of Ennerdale. Numerous other 
intrusions of smaller dimensions have been mapped. 
To what extent any of these eruptive masses were associated with the 
volcanic phenomena remains still to be worked out. There seems to be 
little doubt that a number of them must belong to a much later period. 
Mr. Harker has expressed his belief that the intrusion of some of these 
igneous rocks was intimately associated with the post-Silurian terrestrial 
movements of which cleavage is one of the memorials.^ The Skiddaw 
granite, though it does not touch any part of the volcanic group, but is con- 
fined to the underlying Skiddaw Slates, was erupted after the cleavage of the 
district, which affects the ^'olcanic as well as the sedimentary series. In 
othei instances also, as in that of Carrock Fell, the intrusion seems to have 
been later than the disturbances of the crust." The amount of meta- 
morphism around some of the bosses of granite is considerable. That of 
the Skiddaw region has been well described by J. C. Ward,^ while that of 
the volcanic group by the Shap granite has lieen carefully worked out by 
Mr. Harker and Mr. Man-.'* 
The Shap granite comes through the very highest member of the 
volcanic series, and even alters the Upper Silurian strata. It must thus be 
of much younger date than the volcanic liistory of the I.ake District. It 
presents some features in common with the granite bosses of the south 
of Scotland. Like these, it is later than Upper Silurian and older than 
Lower Carboniferous or Upper Old Red Sandstone time. Its protrusion 
may thus have been coeval with the great volcanic eruptions of the period 
of the Lower Old Red Sandstone. It will accordingly be again referred to 
in a later chapter. 
It must be confessed that none of the large bosses of massive rocks, 
whether diabases, gabbros, felsites, granophyres, or granites, appear to afford 
any satisfactory proof of the position of the vents which supplied the lavas 
and tuffs of the Lake District. Nor can sucli a decided accumulation of 
the volcanic materials in certain directions be established as to indicate the 
quarters where the centres of eruption should be sought. On the contrary, 
the confused commingling of materials, and the comparative shortness of the 
> Quart. Journ. Geol. Soc. vol. li. (1895), p. 144. 2 Oj>. cit. p. 126. 
** “Geology of l^orthem Part of the English Lake District,” Mem. Geol. Surr. 1876, chap. iii. 
Ihc mctamorphism around the diorites and dolerites, and the granophyres and felsites, is described 
in the same chapter, 
* Quart. Journ. Geol. Soc. xlvii. (1891) p. 266, xlix. (1893) p. 359. 
