376 Reports and Proceedings— 
In this paper the Author gives some account of the higher raised 
beaches examined by him on the south-eastern and eastern coast, but 
probably found in other parts of the island also, as indicated by the 
existence of rolled stones, etc. These beaches seem to prove sub- 
mergence (in the case of that at South Hill, to a depth of at least 
130 feet below the present level) at the end of the ‘first glacier 
period.’ 
7 The brick-clay often lying on raised beach, and containing pebbles, 
has been compared to loess by the author. He believes that Prof. 
Prestwich’s theory of sudden and rapid upheaval, with a resulting 
tumultous sweep of water, may be applied to Jersey ; but also, if 
the sinking took place at the end of the Glacial Period, the peculiar 
conditions produced by melting ice may have played their part in 
producing the brick-clays. 
Subsequent upheaval above the present sea-level is indicated by 
submerged forests, sometimes lying on the brick-clay. 
No fossils have hitherto been found in the raised beaches; but a 
bone of Bos primigenius (?) has been extracted from the brick-clay. 
IJ.—June 21st, 1893.—Dr. H. Woodward, F.R.S., Vice-President, 
in the Chair. The following communications were read :— 
1. “On composite Dykes in Arran.” By Prof. J. W. Judd, 
ALS) Wile Gass 
It is proposed to apply the term ‘composite dyke’ to any fissure 
which contains two or more distinct varieties of igneous rock, differ- 
ing from one another in chemical composition or mineralogical con- 
stitution. Such dykes, it is shown, fall into two classes :— 
(A) Dykes in which differentiation has evidently taken place in 
the materials after their injection, as in the examples described by 
Dr. Lawson in Canada and by Prof. Vogt in Norway. 
(B) Dykes in which we have evidence of the re-opening of the 
fissure after its first injection and the introduction of materials of 
totally different composition. It is this class of dykes of which we 
find such interesting illustrations in Arran. 
These Arran dykes belong to the latest volcanic eruptions of the 
British Islands; their analogues are found alike in the South of 
Scotland, and in the North of England and of Ireland. They are 
the infilled fissures along which sporadic volcanic outbursts took 
place after the extinction of the great volcanoes of the Inner Hebrides. 
The subaerial products of these later, and, for the most part, insigni- 
ficant voleanic eruptions, have been all swept away by denudation, 
except at Beinn Hiant and the Seur of Higg. 
The materials filling these dykes belong to two totally different 
classes,—one distinctly basic, with about 55 per cent. of silica; and 
the other markedly acid in composition, with from 65 to 75 per cent. 
of silica. The basic rock is an augite-andesite, which passes some- 
times into an intersertal and occasionally into an ophitic dolerite 
(tholeite and diabase)} ; the glass of this rock shows a great tendency 
to separate from the phenocrysts. The acid rock is often a highly 
vitreous material (‘pitchstone’ or ‘pitchstone-porphyry’) which 
