THE IGNEOUS ROCKS OF THE BEREHAVEN DISTRICT. 
155 
eruptive traps. The contemporaneous traps, the beds of which 
average generally about forty yards thick, are, for the most part, 
at least in their under portions, of a compact greenstone, with here 
and there veins of a light green colour, with small asbestos veins, 
and, in some places, minute crystals of asbestos disseminated 
through it. There are veins of quartz, compact and crystalline; 
also, thin flaky partings in the joints, of opal, of a greenish hue, 
besides crystals of iron and copper pyrites. The copper pyrites 
is only to be found among the asbestos; and, in some places, small 
distinct crystals of felspar and hornblende. 
For about three or four feet of the upper part of the bed, it 
changes its nature, becoming very ashy, and full of small round 
pockets, about a quarter of an inch in diameter, of decomposed oxide 
of manganese; also crystals of iron pyrites. The Dursey Island trap 
seems to be a continuation of one of the Cod Head beds of trap, 
and appears to be confined to the north-west portion of the island; 
but about this it is hard to be certain, as the island for the most 
part is covered with drift and bog, and the coast section is the only 
place affording good data. The bed of trap at the eastern end is 
divided into two by a bed of altered slate, about four feet thick, 
which seems to die out, as it is not to be found as you follow the 
Fig. 1. 
/, Greenstone, 
< 7 , Purple slate. 
h, Green grits. 
i, Purple slate. 
а, Slaty grits. 
б , Ashy greenstone. 
c, Altered slate. 
d, Greenstone. 
e, Bed of altered slate. 
trap on to the west. The higher bed of trap lying on the top of 
the altered slate is very ashy, and resembles the highest portions 
of the beds on the mainland at Cod Head. The lower bed seems 
