29 Kasım 2011 Salı

Prayer Hall Of Friday Mosque at Zaira

  View through the mosque through a north-south axis of bays.
 (Friday Mosque, Nigeria)
The main hall of the Masallaci Juma'a in Zaria is called Uwar Masallaci.
Within the 1500 square meter complex, the sahn occupies about 400 square meters.
This square sanctuary builds upon mosque design popular in Sokoto, which had a flat roof under which a grid of quadrangular bays were supported by pillars.

Also in earlier Sokoto mosque building, the north-south axis of the pillars created a passageway to run along the eastern qibla wall.
Babban Gwani adapted this model by converting the flat roof into an undulating roof with six shallow domes.
The multiple types of roof-bearing stanchions below then are aligned distinctly to mark the differentiations in domes above.
The major load-bearing elements are piers, which are aided by pillars and columns, the choreography of which creates six quadrilateral bays under the domes.
These bays are arranged pairs from east to west, so that the two north-south corridors are composed of three domes each.
 A view of one of the central east-west aisles 
with the joined central piers behind creating a central division.
Four rows of four piers run from north to south carrying the arched cross structure of the six domes. Four of these piers are embedded on both the north and south walls, and the remaining eight piers are free standing to support the central domes.
These two center bays are further supported by another set of eight piers, which are set in pairs straddling the east-west axis centered on the mihrab in the east wall.
The centermost of these east-west piers are joined together around a ventilating shaft which lets out heat through high rectangular apertures in the east and west walls.
These four joined piers create a short wall which divides the central nave and interrupts direct axis to the qibla.
On either side of this wall is a line of empty space which creates two aisles toward the qibla.

The two outer pairs of domes do not join with the east and west wall as they do the north and south walls.
Rather, they are set in from the walls by transferring their weight to three less imposing pillars, one up against each the east and west wall and one shared between them.
This differentiation of space, of the east and west wall aisles from the domed bays, is further clarified by four cylindrical columns, placed at the corners of the central domes.

The main distinguishing feature of the piers is that they carry the bakan gizo arches.
Each pier consists of a sturdy rectangular core which is developed on its long side by twin ribs or bakuna (singular: baka).
Each pair of bakuna has a distance of about four to 12 centimeters between the baka.
These ribs are supported by short horizontal brackets and are corbelled to their apex reaching a height of about 1.8 meters in the two central domes.

Three such configurations of bakan gizos span the north-south axis and are met in the two central domes by two bakan gizos spanning the central east west axis.
Thus, the oblique pressure of the two wider, higher domes facing the mihrab was symmetrically grounded.
The bakan gizos, whose arch flattened near the ground to resemble the curve of a horseshoe, increased stability as well as lightening appearance.
In the west aisle, where the bakuna are lower, the wall is punctured by three windows with transoms supporting the beams of the ribs. Furthermore, the upper parts of the walls are tapered inward which allows them to support some of the stresses.

The bakan gizos cross just under the apex of the tuluwa or vault.
Rectangular panels join the crossing of the pairs of bakuna.
The design of these coffers in the two central domes structurally compliment the crossed ribbing, in that they were carved into a trellis pattern called daurin guga, or securing the water pail, which is taken from the pattern created by lacing rope to create a net.

The coffers in the domes of the four other bays are patterned with azara branches laid together in parallel lines or fit into triangles.
Azara beams, which are cut from the Deleb palm which resists termite infection, are also the structural elements of the arch construction.
The bakan gizos were layered with azaras to form a bracket for the upper layer of masonry.
These are then set within walls which are made up of tubali, cone-shaped sun baked bricks.

The main entrance to the sahn is on the west façade and was strictly for men.
Ten other doorways, six in the north wall and four in the south, provide cross-ventilation and sufficient light.
Further light is accessed through small vertical slits in the upper regions of the walls.

The undulating roofline, with the symmetrical soft swells of the domes compliments the lines of the gently tapered yet rectilinear mud walls.
Interior divisions can be visually marked on the roofline by pointed pinnacles which are positioned beside grooves cut into the roofline for drainage and which counterbalance the height of the pinnacles.
The roof is accessible by an external flight of steps from the south west corner of the sahn, from where the call to prayer was also done.

The mihrab creates the only exception to the sahn's symmetry.
The mihrab projects from the east façade of the sahn in a rectangular dual chambered vestibule which then opened into the eastern part of the haraba, which could have been the Emir's means of entry from his palace.

The decoration within the sahn building primarily arises from the underlying patterning of the structural elements.
The bakan gizos and the walls were all plastered so that their lines are revealed in the molding.
The walls are sculpted with rectilinear shapes, the upper tiers of the columns are encircled with horizontal grooves, the corners of the square pillars were profiled with vertical incisions in effect flattening their tapered, concaved lower segments, and deeply incised verticals, triangles and circles intermingle together on the piers.
Horizontal lines in the soffits of the arches serve to elongate the form of the bakan gizos.
The bakan gizos were further vertically accentuated by chevron like arrows leading the eye upwards.

There is a strong contrast between light and shadow in this building so it is only possible to view a few different motifs at any particular place.
The decoration on the architrave surrounding the mihrab niche on an otherwise undecorated wall, is particularly complex and together with the bold designs on the adjacent pier faces, draw the eye to emphasize the mihrab.

Though the interior detailing today is mostly the white color of the plaster used, like the Emir's Palace at Kano, the interior of the Masallaci Juma'a was painted with a plaster mixed with mica.
The sheen was much more discreet than that at Kano, and today it has completely worn away. Supposedly, the wet plaster of the flat surfaces of the walls and piers were once intagliated with a herringbone design, which was then painted with the mica and then scratched from the raised part of the design, leaving a reddish-brown relief with the grooves creating a silvery background sheen. Today the walls are coated by cement plaster, and decoration is no longer hand done and reveals more repetition.
Furthermore, it is likely that the relief patterns before the twentieth century were more sober than some of the Arabesque influenced designs seen inside today.

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