On Hollow Spherulites in ancient British Lavas. 391 
margin of the granite promontory there was a striping of light and 
dark bands, the colour of the latter being due to the abundance of 
black mica. The gneissic structure was attributed to lateral pres- 
sure, the existence of which in the associated strata was seen in the 
conyersion of grits into schist-like rocks, in the production of 
cleavage in beds of coarse materials, in the crushed condition of 
some masses, in the overthrow of folds, and in the production of 
planes of thrust. The direction of the pressure was perpendicular 
to the planes of foliation in the granite. 
The schistose rocks of the region were divided into two groups. 
The Lough Foyle series consisted of quartzites, quartzose grits with 
a mineralized matrix, slaty-looking schists, fine-grained satiny 
schists, black phyllites, and crystalline limestones and dolomites. 
The semicrystalline condition of most of these rocks was character- 
istic. This series was well seen at Londonderry and on Lough 
Foyle, and formed a broad band striking to the south-west. These 
rocks were compared with similar types in the Hill of Howth 
(north of Dublin), near Aughrim (co. Wicklow), and south of Wex- 
ford. ‘The Leinster semicrystalline masses were quite unlike the 
Wicklow Cambrians, and bore a strong resemblance to the slaty 
series of Anglesey. They were lithologically intermediate between 
the Donegal and Anglesey groups, and from a comparison of all 
these areas the author referred the Lough-Foyle Series, with some 
confidence, to the Pebidian system. The prolongation of the Lough- 
Foyle rocks into the Grampian region was well known, and Ireland 
thus served to connect some parts of the Scottish highlands with 
South Britain. The author was not prepared to correlate this 
Donegal series with any American group; but the lithological affi- 
nities were rather with the Taconian than with the Huronian. 
The Kilmacrenan series, in which the granite is intrusive, was 
described as crystalline and older than the Lough-Foyle group. It 
was mainly made up of micaceous, quartzose, hornblendic, and hydro- 
magnesian schists, quartzites, and crystalline limestones. There 
were no indications in these rocks of a metamorphism progressive 
in the direction of the granite. This series was lithologically similar 
to the Montalban system. 
Fifty-five microscopic slides of Donegal and Leinster rocks had 
been examined by Prof. Bonney, whose observations confirmed 
those of the Author both as regards the nature and relations of the 
granite and the general characters and state of crystallization of the 
two schistose groups. 
2. “On Hollow Spherulites and their occurrence in ancient 
British Lavas.” By Grenville A. J. Cole, Esq., F.G.S. 
Many of the felstones of North Wales have been shown to be altered 
lava-flows of an originally glassy type. In several localities, as in 
the Pass of Llanberis, at the foot of the Glyder-fawr, these rocks 
- contain numerous nodular bodies, from ;+, inch to some inches in 
diameter. ‘The smaller varieties have the appearance of spheru- 
lites, but the larger are very often hollow, their cavities being 
partly filled with minerals deposited by infiltration. The lavas 
