Keegan: The Rocks of Patterdale (Uliswater). 9 
Place Fell above Side Farm, and also on portions of Bleas Fell 
and the ground to the north of that hill. Generally speaking, 
the volcanic ash of the lake district rocks is distinguished from 
the lava by the fact that the so-called ‘ground-mass’ is nearly 
always irregular and with no definite structure; it contains no 
acicular crystals or even distribution of magnetite grains, though 
sometimes chloritic matter occurs along lines of flow ; moreover, 
the larger ‘ porphyritic’ crystals are, as a rule, almost always | 
corroded, broken, or unshapely, and no definite ‘pelaseepship can 
be traced between these and the altered ferro-magnesian minerals 
or the ground-mass: wherein they are imbedded. he sam 
secondary or alteration products can in general be detected in 
the ashes as in the lavas, but in the former there is evidently 
a much larger amount of clear and darker green chlorite than in 
the latter. Slides prepared from the ash-slate of Place Fell 
quarry show a very large number of whitish turbid forms of 
an approximately crystal shape, which are composed mainly of 
calcite after felspar, but there are one or two clear and glassy 
ones of the latter mineral fresh and unchanged; along with these 
we observe a much smaller number of clear chlorite crystals. 
doubtless after augite, but the original contours are lost and 
abra ed. ese larger constituents are immersed in a powdery 
_ ‘base’ much more injured and disordered than they are, it being 
: hee raed and composed of a semi-opaque heterogeneous 
' bestrewn with patches of chlorite, dark brown oxides 
of i iron, etc.; and ‘we may look upon it that the original andesitic 
and other volcanic dust of the rock has decomposed in such 
manner that the augite, etc., gave rise to chlorite with garnet, 
ne while the felspathic part of che mixture was largely altered to 
mica’ (Hutchins). A rock from the ground north of Bleas Fell 
is a very good example of this volcanic ash. Moderately large 
crystals, broken, deformed, and corroded, and nearly all altered 
to calcite, jostle against one another with only small seams and 
intercalations of a dark speckly ‘ base,’ while, intermixed with 
_ these, there are a goodly number of clear non-pleochroic chlorite 
forms about the same size, and appearing deep blue under 
crossed nicols, together with large patches of oxide of iron. An_ 
ash rock near at hand is very fine-grained, and is made up of 
avery fine speckly matter with the usual sennkliay of chlorite. 
dN specimen from an old quarry on Bleas Fell showed a similar 
hh 
, 
x hibiting, however, the usual calcareous alteration es 
ose st a oo and more Bites gigi ‘amount neon e 
heterogeneous conglomerate, but with smaller constituents, _ . 
