Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/27

 Rh have been washed out of them, are, coarse yellow, brown, red, and green jaspers, sometimes containing veins of iron ochre, or crystals of hornblende, or passing on the one hand to quartz, and on the other to hornstone. Sometimes they are veined with quartz, and striped and waved of various colours, with mixtures of quartz and chalcedony, resembling agates.

The Peninsula of Little Sercq is connected with the main island by the high narrow ridge before mentioned. This is about three hundred yards in length, and has a precipitous face to the sea on the eastern side; to the west it is also partly rocky and precipitous, and the remainder is a steep declivity of broken rocks and rubbish. It is called the Coupée, and on the top of it is a rugged path of frightful appearance, being in many places not above a yard or two in breadth, and in most without boundary on either hand. By this, the communication between the two parts of the island is kept up.



This narrow neck is traversed by a vein of porcelain clay at its widest part, ten or twelve feet in thickness, and lying E and W across it.

In most places this vein is much contaminated by purple, red, and yellow oxides of iron, and intersected by reticulations of quartz, which are probably the remains of veins running through the granite, from the decomposition of which the porcelain clay appears to have originated. Grains of quartz are also found dispersed through it, and indeed in many places it seems to be little altered from its original granite. Towards the bottom of the vein various substances are found among which are coarse approaches to chalcedony and agates; but the greater and apparently the most interesting part of the vein was inaccessible to me, in consequence of huge masses of fallen rocks.

In some places are veins of quartz having a slaty fracture, and becoming earthy, or much discoloured with iron, or containing