200 CHILI. 
vertically to a depth of about one hundred and fifty feet. Each 
person was provided with a tallow candle, stuck in the end of a split 
stick six feet long, and caution was given not to lose sight of the 
guide, for the galleries, although small, are so numerous, and commu- 
nicate with each other so frequently, that a person might easily be lost. 
The ladders, or rather posts, by which the descents are made, are 
not a little dangerous. They are not all secured, so that it becomes 
necessary for one person to hold the ladder whilst another descends, 
and it causes no small uneasiness to see the foot of it resting on a 
mere ledge. These shafts are at times crossed by a gallery, where 
but a single post is laid over them, and they pass over it by steadying 
themselves against the side wall. At the bottom of one of the shafts, 
at about three hundred feet from the mouth of the mine, the thermo- 
meter, after remaining for half an hour, stood at 52°, the air outside 
being 56°. This may be considered a fair test of the temperature. 
They report that they perceive no difference in the mine, in winter 
and summer. 
There appears to be little system in working the mines, and little 
knowledge of the structure of the rock or the courses of the veins. 
Mr. Alderson mentioned that a few months previously, they had been 
working for several weeks, extending a shaft, without meetino- a 
particle of ore to repay their labour, and they were just about givino- 
up the search, when the mayoral, or master-workman, declaring he 
would have a last blow for luck, struck the rock with all his force. 
This detached a large fragment, and to their surprise and delioht, 
laid open a vein which proved the largest and richest that had been 
worked for many years. From this it would appear that the employ- 
ment is attended with much uncertainty, and after exhausting one of 
these treasures, there are no means or signs known to them by which 
they can ascertain the best direction to take to discover another. 
This mine is situated in claystone, the sedimentary rock of the 
region, where it is intersected by a dike of compact clinkstone. 
The dike is about six feet wide. The adjoining claystone has a 
dark greenish brown colour, and resembles a wacke. It is so much 
fissured that it is difficult to break off a small piece which will 
present a fresh surface. The green carbonate of copper, and silicious 
carbonate of copper (chrysocolla), stain the rock for one hundred feet 
from the vein, occupying the fissures, and giving the surface a green 
or bluish tinge. In some places chrysocolla forms in small botryoidal 
incrustations on the face of the rock. The ores of copper occur in 
