OBSERVATIONS. 
9 
mixed with arfenic and interfperfed 
through yellow copper ore j thefe are 
from Poldice. The tin ores from Huel 
Brea Load, in the parifh of St. Ives, and . 
from Cornellow Cliff, in Zennor, are 
united to fhoerl. In thofe from the 
former place the tin-ftones are like a 
heap of cryftals of different fizes inter¬ 
woven with a compact, finely radiated 
greenifh grey fhoerl neftways in granite : 
But from the latter place I have fpeci- 
mens of blaekifh Zinnzwitter in a vein 
only half an inch thick, the walls of 
which are a fine fhoerl. 
In another tin vein at Pelmine, in the 
parifh of St. Agnes, the thicknefs of 
which is one inch and a quarter, both 
walls confift of pretty large tin cryftals of 
a light greyifh yellow colour, by means 
of which the vein is very evenly feparated 
from the rock: the fpaces between the 
tin cryftals are filled up by a reddifh white 
Tin- 
