10 The Quicksilver mines of Almaden, Spain. 
The veins in the upper workings appear to have been ve 
indistinctly defined, but have increased in power and in quality 
of ore steadily as greater depths have been reached. They were 
fully developed 1 in their true character only on the 5th floor, 
while now in the bottom of the mine at the 10th level the 
richness and abundance of the ore in sight exceeds all before 
known. The following tabular statement illustrates this pro- 
gressive increase in the extent and width of the three veins at 
several levels commencing with the fifth. 
San Diego. San Francisco. San Nicholas. 
Level. Length. Width. Length. Width. Length. Width, 
5th, 164’ 14°5’ 426’ 13. 98' 9°6' 
6th, 264 16°5 363 49°5 2145 10°7 
ith, 495 15°3 511 15°3 412 13°2 
8th, 561 26°4 594 14°5 610 18°1 
9th, 495 21°5 478 9°1 561 9°2 
- The 10th level is not yet sufficiently worked to determine 
the length or thickness of the veins, but the ore is of fine qual- 
ity, The veins stand nearly vertical and are opened by verti- 
ne shafts. Their course is in general N.W. and §.H., and they 
separated from each other by slate and sandsto tone. The 
fieae extent of these veins is far from being completely proved. 
Work has been suspended where the ground became compara- 
tively sterile. But it is well known that the mine, extensively 
opened in the 17th century by the Fugger Counts, exists in 
close proximity on the N.W., while a few yards of exploration 
in that direction, or to the 8.E., may show the veins restored to 
fruitfulness. The great mine worked by the Fuggers, and 
after them until the great fire of 1755, though in close prox- 
imity to the present mine, is now wunknown, although the records 
aay its great yield and that it was worked to a depth of 825 
‘The mode of extraction of the ore with the securing of the 
mine is by leaving alternate pillars of the solid ore 4 varas wide, 
the space bar void between which, after the ore is removed, is 
filled by masonry, or by broken stones supported upon arches 
ny, ae galleries of the mine are also turned in ma- 
sonry. This system was adopted in 1804 on account of the 
scarcity of timber and with a view to the greater permanency 
of the work. The reserves of ore thus accumu ated, equal 
since 1804 until within the past ast 6 years, since which time very 
, ve been removed, the spaces left 
; wine less care than the first set of pillars. 
umber is used only for tee urposes; the sto uired 
for the ‘i fi igh athe 
masonry eo in the adjacent 
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