Marble lines and bands
Between many stationes in all three porticos are thin lines or strips,[1] and somewhat broader bands,[2] made of pieces of marble. These marble separations occur in the front rooms only. A few mosaic lines may imitate marble lines.[3] Often the marble is on the axis of the central column, so precisely in the middle between two stationes,[4] but quite a few were shifted to the north or south, or east or west.[5] Sometimes the pieces are quite irregular and may be an ancient restoration.[6] Conclusions from the lines and bands should be drawn with caution, because of missing stretches of floor between the stationes, and because of ancient changes and restorations.
Presumably the separations were placed by those responsible for the square, the city council. A grid was laid out, using the brick columns as markers of separations. The marble lines and bands bordered something, and it is unlikely that this was a generic floor, also laid by the city council, of bipedales, travertine slabs, marble slabs, or mosaic. The lines and bands would have been of little or no use. They are however a suitable solution for separating specific mosaic panels, especially because these could be modified or replaced in the course of time.
In the Hadrianic period the porticos already had a commercial character, witness the earlier mosaic of the stuppatores restiones at the lower level, the sacomari linked to the Altar of the Origins of Rome, and the inscription NAVICVLARI AFRICANI, which is not later than Hadrian. There might therefore have been specific Hadrianic mosaic panels, each belonging to a group of people. However, no Hadrianic mosaics have been preserved. Had they existed, then surely some would have been kept in use or partly reused. In other words, there was a generic Hadrianic floor, presumably of stone or terracotta slabs, and the marble lines and bands were added later, when the Hadrianic floor was lifted.
The oldest mosaics on the upper level of the square are those of Alexandria in stationes 26-28, dated to ca. 150-170 AD by Becatti and Clarke on stylistic grounds. They have marble borders. We may safely assume that the whole grid was laid out shortly before these mosaics were laid, not just this part, which would have served no purpose and actually hampered the mosaicist working in stationes 26-28. But this is problematic. It is strange that it took forty years or so before other mosaics were added on the square, in the period ca. 190-210 AD. The best solution seems to me that the mosaic in stationes 26-28 was also laid in the period ca. 190-210 AD. This is not to say that the stylistic dating of ca. 150-170 is wrong: it may well be correct. Alexandria was of special significance, not only because of the goods that it exported to Rome, but also as cultural capital of the Mediterranean world. As much as three stationes were allotted to Alexandria by the city council. It causes no surprise that the Alexandrians did not choose for the new, sketchy style, but wished to continue an old-fashioned style, commissioning an older mosaicist.
Mosaic lines and bands
There is also a great variety of framing lines and bands made of black mosaic tesserae. They surround depictions and entire rooms. The width varies greatly, from thin lines to very thick bands. The interpretation of these frames is complicated due to many ancient restorations and modifications. Apparently considerable deterioration over a prolonged period of time was accepted, before restoration was begun. We must also reckon with functional changes, such as the departure of a group of shippers, followed by the arrival of shippers from another city. The mosaic frames did not form a grid in its own right, but should be studied together with the rest of the mosaic, the entire room, and the neighbouring rooms.
The dividing walls
An inspection of the dividing walls in situ has not yet taken place, so what follows is preliminary. There are quite a few discrepancies between the plans published by Vaglieri (presumably made by Gismondi) and by Gismondi (in Scavi di Ostia I), and especially between these plans and the current situation. All of these are described in the catalogue of the stationes. Partly the differences may be due to the state of preservation and to the loss of some masonry after the excavations. The differences are not shown on the main plan, which shows the current situation, but can be recognized by comparison with Vaglieri's plan and with the scan of Gismondi's plan.[7]
Secondary dividing walls are found in the back rooms only. Most of the walls are very thin (ca. 0.30). They are usually set against the centre of the central brick column, some are off centre. The walls are not load bearing, so it is surprising that a few have a double width. Perhaps it was deemed necessary to provide some extra support for the beams of the ceiling.
The walls were set on top of the mosaics, without a foundation. They are made of opus latericium (bricks), opus vittatum simplex (oblong tufa blocks), and opus vittatum A and B (respectively with a 1:1 alternation of oblong tufa courses and brick bands, and in different alternations). There are obviously several phases. Vittatum A is seen in the north-west part of the square only.[8] Opus latericium is seen on the north side of the square and in statio 59 only. About the date we can say that the opus vittatum B walls belong to the second half of the third or fourth century - they are not earlier than c. 250 AD.[9]
Because the walls occur in the back rooms only and, generally, neatly follow the boundaries between the stationes, we can conclude that they belong to the commercial phase of the square.
For the east porticus we can add the following. It has been suggested by some that the dividing walls of bricks and tufa stones replaced wooden partitions. Here it should be noted that the only stationes without a dividing wall have a door in the back wall, which "overlaps" the central brick columns. This indicates that when the back wall was built (during the reign of Domitianus) dividing walls or partitions were not foreseen here.
The southern wall in statio 10 has a kink, making the back part of the room wider. According to an old plan there was a similar kink in the north wall, which however is not present in the current wall. In the back wall of stationes 10-14 is a row of small beamholes, passing through the wall, at a fairly low height from the floor. These are presumably putlog holes for the scaffolding used during the construction.[10] Between the front and back room of statio 20 is a wall of opus vittatum B. This wall might in some way be related to the presence of a door in the back wall, or to the presence of cities on Sardinia in the neighbouring stationes 19, 21, and perhaps 22.
For the north porticus we can add the following. At the west end a small room was created in the back part of the back room of statio 37. It had a door in the centre of the south wall. The walls are of undated latericium. It is mostly modern.[11] The room may have been a special office or a small shrine. At a later date the small room was enveloped by a larger room, consisting of the back rooms of stationes 36-38, with a door in the passage between the front and back room of statio 37. The walls of the larger room are of undated opus vittatum.
For the west porticus we can add the following. A room was created in the back part of the back rooms of stationes 43 and 44. The north and east wall are of rubble masonry with small tufa blocks. The south wall, which continues in the remainder of the back room, is of opus vittatum A. At the west end of this wall may have been a door. The mosaic resting on the final raising was removed (the remains were found below the later walls). A new mosaic, of which only a fragment was found, was laid in the room at a somewhat higher level. Pohl's plan shows a dividing wall inside the separate room, creating a north and south half. It is not visible today. Finally, the entire back room of statio 59 was changed into a walled room (an archive?). The walls are of opus vittatum simplex, opus vittatum B and opus latericium. In the north part of the east wall is an opening with a reused threshold for a door opening inward.
The motivation for adding the dividing walls and small rooms is not obvious. The main architecture and lay-out of the square remained intact, so there is no reason to think of a shift in or change of function. There may have been practical reasons for the dividing walls, if only against the draft. The porticos had always been open for circulation of people. It is quite natural that the need was felt for partition walls between the back rooms, where the shipping business was discussed.
(1) Thin lines or strips: 7south, 9south, 11south, 11north, 13south, 23west, 23south, 28east, 33east, 36east, 36west, 38east, 57south.
(2) Thick bands: 26east, 26west, 31west, 33west, 38west, 44south, 52south, 57north.
(3) Mosaic lines: 10south, 40south (?).
(4) On the axis of the central column: 7south, 9south, 11north, 13south, 23south, 26east, 28east, 33east, 33west, 40south (?), 57south.
(5) Shifted: 10south (to the south), 11south (to the south), 26west (to the east), 31west (to the east), 36east (to the east), 36west (to the east), 38east (to the west), 38west (to the west), 44south (to the north), 52south (to the south), 57north (to the south).
(6) Possible ancient restorations: especially 33west, which also contains a piece of red stone or terracotta.
(7) Layer 0 on the CAD drawing.
(8) Opus vittatum A: 45north, 45south, 46south, and perhaps 36east.
(9) On opus vittatum see most recently David - De Togni 2019.
(10) On putlog holes in Ostia see Booms 2007. Between bricks they usually measure 0.08 x 0.08 or 0.10 x 0.10.
(11) There seems to be a predominance of yellow bricks, also seen in the rooms to the north of the north portico. The colour of the bricks might point to an Antonine date.