Prof. T. G. Bonney—Pebbles in the Bunter Beds. 201 
observed that in some slides the bubbles were steady, while in others 
they vibrated briskly, though I could not discover any difference in 
the circumstances to account for this. Microlithic inclosures of ferrite, 
opacite, and perhaps brown glass are noticed. 
The felspar crystals are commonly much decomposed and ferrite- 
stained, in some cases more or less replaced by microliths. In one 
specimen the whole crystal is a felted mass of a colourless flaky 
mineral, which is very probably a hydrous mica; in another the 
replacing mineral more nearly resembles my section of a typical 
pinite. : 
Tourmaline is conspicuously present in three of the specimens. 
It occurs both in scattered tufts of an acicular pale indigo-blue 
tourmaline, and in larger crystals of brown tourmaline. The former 
are most abundant in the slide where this mineral is a conspicuous 
constituent of the ground-mass, and some of the larger of these are 
surrounded by clear quartz, as I have already described.’ In one 
the tourmaline is much clouded with opacite. In one or two speci- 
mens brown mica and possibly hornblende may be detected. 
Two specimens contain a ferruginous mineral which often decom- 
poses and falls out, leaving small cavities. As this usually grinds 
away, I have not been able to ascertain to what to refer the original 
mineral; it appears now to be ferrite associated sometimes with 
granules of quartz, and with a felted mineral like a mica. 
These rocks then, as plagioclase felspar does not appear to be a 
common constituent, may be properly designated as quartz-felsite 
(quartz-porphyry). 
Of the three specimens which exhibit a more or less spherulitic 
structure, one has a crypto-crystalline ground-mass consisting of 
rounded aggregates of crystallites composed of quartz and (probably) 
a decomposed ferrite-stained felspar, which are intercrystallized in 
irregularly radiate bunches. The crystallites are slightly wavy, so 
that the spherules resemble tufts of diverging roots rather than, as 
is very commonly the case, of diverging rays. Spherules have fre- 
quently a sharply distinguished outer zone, in which the ferrite 
staining is markedly darker. In the interstices microcrystalline 
quartz and felspars (decomposed) may be seen ; there are a few small 
irregular quartzes with numerous very minute cavities—empty, so 
far as I can observe. 
Another specimen has a crypto-crystalline ground-mass with the 
spherulite-structure less distinctly marked. This one is more distinctly 
micro-porphyritic. The quartzes, generally rounded externally with 
many inlets and inclosures of the ground-mass, are bordered with a 
zone above ‘01 in. wide exhibiting an imperfect radial structure. 
They contain minute empty cavities, and glass or ‘stone’ inclosures. 
In this specimen all the felspars exhibit the twinning of plagioclase. 
The extinction angle between successive lamine is a large one, as 
much sometimes as 31°, when the plane in the case of the smaller 
extinction angle makes an angle of 13°, with a vibration plane of the 
polarizing apparatus. These also contain numerous crystals of a 
1 In Luxultianite, Mineralogical Magazine, vol. i. p. 216. 
