172 Copper Mines of Chili. (April, 
Its shaft attains a depth of 220 fathoms. An aneroid 
barometer indicated a vertical depth of 1ooo feet. The 
total length of the shafts, wings, and levels is about 
7 miles. There are employed on Company’s account fifty 
barreteros (miners); and 150 tributers work on their own 
account in the abandoned upper workings. 
The mine is supplied with good hauling machinery, 
worked by a 15 horse-power engine. In all the mines in 
this minerale great care is taken to condense the steam. So 
perfectly is this done, that at the Mondaca 5000 gallons 
monthly replace the loss in making steam and supply 
the wants of the establishment. 
The mine is admirably worked. The levels are straighter, 
the shafts loftier, the timbering is better, and the explora- 
tory work is further ahead of the stopes than in any of the 
Tomaya mines, thanks to the wisdom of the principal 
owner, Don Ramon Ovalle, and the skill of the manager, 
Mr. McAuliff. But the same is generally true of all the 
large mines in this region; due probably to the fact that 
they have been systematically worked only since the intro- 
duction of European methods of mining. 
At surface and for some 60 fathoms below the lode is 
narrow ; but here a branch, supposed to be the Veta Santa 
Rosa, falls into it, and it bulges suddenly to tremendous 
size. So at intervals it alternately contracts and expands: 
here diminishing to a yard in width; there bulging to six or 
- seven times that size. The largest excavation in the 
Mondaca mine is 260 feet deep, 180 feet long, 45 feet wide. 
‘Twenty-one miners have worked abreast upon a solid face 
of ore. At about 120 fathoms from surface magnetic 
pyrites comes to preponderate so largely that for many 
fathoms the lode is left standing; but good yellow sul- 
phuret of copper has reappeared in the central chimney of 
ore, and it is hoped the mine will resume its former 
richness. No banded struéture is observable. The copper 
pyrites, mixed with quartz, magnetic pyrites, common 
pyrites, and a trace of blende, being mixed irregularly 
through the lode. A clay selvage occurs on the floor of the 
lode, and on the hanging wall a mineral resembling 
compact asbestos. 
Although the lode is not producing as well as in the 
upper levels, the yield has not fallen off, so great are the 
reserves of good ore left to draw upon. ‘The following 
table of the expense and production from 1862 to 1870, 
kindly furnished me by Mr. McAuliff, gives a good idea 
