201 
Geological Relations cf the East of Ireland, 
about ninety fathoms lower do#n it encounters Glendalough vein, 
among the granite precipices. So far as hitherto explored, this vein 
appears in general to be five feet wide, but in one place it is enlarged 
to the breadth of twelve feet. It dips 65° toward the west. The 
predominant veinstone is quartz, which is firmly adherent to the 
hard solid eastern granite wall; but on the west or hanging side, 
(which, however, is also smooth and well defined), the granite, 
though to the eye it appears firm, is commonly soft, giving way to 
the pressure of the fingers, and it is thus sometimes affected for a 
distance that varies from a few inches to two and three feet from 
the vein, where the rock at length resumes its usual degree of 
solidity. Between the hanging wall and the vein, is a sticking, and 
between this and the quartz mass on the eastern wall, the ingredients 
present various degrees of solidity, being sometimes quite loose, 
sometimes very compact. They frequently consist of well defined 
fragments of firm or of softer granite, more or less consolidated and 
cemented by quartz, heavy-spar, blende, and galena. Heavy-spar 
occurs however only in small quantities, and chiefly toward the 
hanging wall ; and fluor-spar I have observed only once dissemi- 
nated in quartz, or in small cubical crystals of a pure white colour, 
occupying with quartz crystals a cavity in the quartz, which at 
times abounds in drusy holes, or lough-holes as they are called by 
the miner, from their frequently containing water. 
This vein has yielded, in some parts of its course, in the cubic 
fathom, from three to four and a half tons of galena, which appears 
either in layers parallel to the walls, or in disseminated masses. 
The former are more particularly confined to the eastern side: white 
lead ore also occasionally appears in acicular crystals, and likewise 
green lead ore, but the latter is seldom found except near the surface. 
Blende is not uncommon, and copper pyrites appears casually dis- 
Vol. V. 2 c 
