FROM THE KENDAL AND SEDBERGH DISTRICTS. 175 
finely, and felspar has been the principal constituent, but that the 
forms of the crystals have been almost obliterated by decomposition. 
So far as can be inferred from the outlines still to be traced, they 
most probably were plagioclase. In this ground-mass crystals of bio- 
tite abound, up to about :03 inch in diameter, and numerous grains, 
as usual, of another mineral. These grains are traversed by irregular 
eracks, lined with a filmy olive-brown serpentinous mineral, and 
rather resemble altered olivine ; but two or three fairly well preserve 
the outlines of augite. In some the other replacing mineral is cal- 
cite (or dolomite), in the majority the granular (? serpentinous) 
mineral mentioned above. We may then class this rock as a 
decomposed kersantite*. 
(10) Uldale Heady. 
Characters.—Macroscopic. A compact dull brownish-grey rock, 
containing many small crystals of biotite, and a few small pale-grey 
crystals. In another specimen (which seems more decomposed, and 
is of a paler colour) the mica crystals occasionally attain a larger size, 
one or two being about 0°25 inch. 
Microscopic. The ground-mass of this rock appears to consist of a 
glassy base crowded with microliths. These are :—(a) colourless 
microliths, probably felspar, and possibly, in some cases, augite ; 
(6) brown mica ; (c) ferrite and opacite. In this base are scattered 
larger grains of iron peroxide (? hematite), the usual crystals of bio- 
tite (rather free from enclosures), and a nearly equal number of 
grains and crystals of augite, altered in the usual way, but in one or 
two cases showing the characteristic outline of the section perpendi- 
cular toc. One of these contains acicular ferrite, which has been 
arranged parallel to the planes of prismatic cleavage ; but most are 
clear. The decomposition-products are rather variable, but there is 
little calcite or dolomite. Plagioclase is not certainly recognizable ; 
but (so far as an opinion can be formed from microscopic exami- 
nation) the rock is probably a kersantite-porphyrite. 
It is intrusive in Coniston Grits, forming a dyke probably some 
yards wide, but the sides are not exposed. It is generally much 
decomposed, being in places almost a sand. Fragments of the 
Grit are occasionally included. 
(11) Holbeck Gull. 
Characters—Macroscopic. A rather pale reddish-grey, dusty- 
looking rock, containing numerous small crystals of dark mica, with 
rather silvery lustre and a few pale-green specks. On a polished 
surface it has a minutely crystalline aspect. The rock is much de- 
composed ; external surfaces are rather redder than the rest. 
* I believe this specimen to be from a dyke in Coniston Flags, but have no 
information beyond the label on the specimen, which has been in my possession 
for some years.—T. G. B. 
t E. of River Lune, considerably to N. of the general line of those we are 
describing. 
