488 
HARKER : LAKE DISTRICT IGNEOUS ROCKS. 
well-banded fine tuft's and volcanic breccias. The tuffs 
are finely laminated and sometimes contorted. In places 
they have been converted into a kind of hornstone. The 
breccias contain fragments of various volcanic rocks, and 
are often of coarse texture. The recognisable fragments 
vary. About Sty Head and some other places a consider- 
able thickness of breccia is characterised by angular fragments 
of pink compact rhyolite ; in other places basaltic fragments 
prevail. Both tuffs and breccias often contain little red 
garnets, easily visible to the eye. These are probably of 
metamorphic origin ; but some of the intrusive rocks of 
the district also contain garnets, which there seem to be 
a primary constituent. Garnets, it may be remarked, 
are especially frequent in a puzzling set of rocks occurring 
immediately below the Scawfell group, and considered 
by Mr. Marr to be intrusive : these will not be discussed 
in this place. (2) The fragmental group (tuffs and breccias) 
reappears further south in a highly-cleaved condition, and 
is extensively quarried for slates. These are too well known, 
as regards their general appearance, to require description. 
Most of the rocks of this group are of medium acidity, but 
both basic and acid varieties are represented, according to 
the preponderance of one or other kind of material among 
the constituent fragments. 
{(1) Shap Andesite Group. — This higher group of andesites forms 
a strip running from Torver, near Coniston, to the Shap 
granite. The rocks are amygdaloidal augite-andesites, 
hypersthene being apparently absent. 
(e) Shap Rhyolite and Yetvdale Breccia Group— This group 
forms a strip immediately south of the preceding. The 
rhyolites are of very compact appearance, and rarely show 
any conspicuous porphyritic crystals (never porphyritic 
quartz). They are sometimes grey and rather flinty looking, 
sometimes duller with a pink or cream colour. The micro- 
scopic structure is variable, and depends largely upon 
secondary changes ; some A-arieties, as about Stockdale, 
