La pedra en sec. Materials, eines i tècniques tradicionals a les illes ...

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** *: 6 6.3.5 DRYSTONE MASONRY STRUCTURES
UNDERGROUND
SPRING PASSAGE
Description
Walled gallery dug to reach the water
table for and the withdrawal of water
by gravity.
Uses
To obtain water for irrigation and for
human and animal consumption.
Site
The springs in the examples are on
plains used for fruit and herbaceous
crops (example 3), next to torrents
(examples 1 and 2), and built into the
terraces farmland (example 4).
Type of gallery
The examples are either underground
passages dug out of the ground
(examples 3 and 4) or underground
passages which also make use of a
torrent channelling wall as a side wall
(examples 1 and 2).
Gallery roofing
The most common ways of roofing an
underground passage are lintel roofs
using stone slabs (example 3) and
roofs made of stones placed on end
which in most cases form barrel vaults
(examples 1 and 4) or ogival vaults
(example 2).
Access to the gallery
Access is usually made through a single
opening which can be entered
with varying degrees of ease. Long
underground passages have airshafts
through which material can be lowered
or raised (examples 2, 3 and 4)
and in some cases these shafts have
roofed stairs by a drystone masonry
structure (example 3).
How the Water is Piped Through the
Gallery
Along tiled grooves (examples 1 and
4) or stone channels (examples 2 and
3) running next to one of the walls
(examples 1, 2 and 4) or down the
middle of the underground passage
(example 3).
Materials
Limestone (examples 1, 2 and 4),
sandstone and limestone (example 3).
Accessory Items
Steps leading down to the opening of
the underground passage (example
2), water accumulation structures outside
the mine (example 1), and channels
outside the gallery to carry water
to small reservoirs (examples 1 and
4).
Location
Ses Cases Naves, Deia (example 1);
font de sa Capel-Ieta, Valldemossa
(example 2); Son Olesa, Valldemos-sa
(example 3); Son Moragues, Valldemossa
(example 4) ..••