A 13th-century hydraulic ore mill at the mining site of Brandes (Isère), France

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Introduction
The excavation of the 13th-century ore mill presented in this paper was carried out in the framework of a research program focusing on the industrial quarter of the mining town of Brandes (Isère, France). The site, under study since the 1980s, exploited argentiferous veins between the late 11th century and the first half of the 14th century in the Oisans Mountains at an altitude of 1,800 m (Bailly-Maître et al. 1994).
Grinding is an important stage in the operational sequence of polymetallic production to enrich the ore (lead, copper, silver). It takes place between the phases of mining and reduction and is intended to separate the impurities from the gangue. In Roman times, although there is evidence of grinding ore with rotary hand querns (Pulou et al. 1997), no hydraulic ore mill has been brought to light. Furthermore, only two such installations are known for the Middle Ages (Benoît 2014). The Abstract: This paper presents the results of the excavation of an ore grinding watermill brought to light in Sector B 121 of the industrial quarter of the mining town of Brandes (Isère, France). The mill, dated by dendrochronology the 13th century AD, was driven with water channelled from the Font-Morelle spring. The head-race and spillway are examples of the opportunistic reuse of earlier anthropic (canal and mining trench) or natural (faults and karsts) features. The tail-race was not totally excavated. The mill-house (drywall and timber construction) is poorly conserved and the millstone driving mechanisms are difficult to interpret. A series of features suggest the use of a horizontal water wheel driven counterclockwise by a jet of water guided through a flume. A large number of millstone fragments and flakes were studied in a previous article.

Nicolas Minvielle Larousse
Nicolas Minvielle Larousse, archaeologist and historian, Aix-Marseille University, CNRS, LA3M;5, Rue du Château de l'Horloge, BP 647, 13094 Aix-en-Provence, France. Ecole Française de Rome, Piazza Navona 62, 00186 Rome, minvielle.nicolas@gmail.com first, dated to a 13th-14th century, was excavated at a mining site in the Czech Republic in the 1980s (Kurdnáč 1992). Unfortunately, its study does not offer any details except a photograph of the mill's foundation on posts and a millstone dressed with furrows. The second medieval mill, excavated at Pampailly (Rhône, France) in the 1990s (Benoît 1997), unfortunately remains unpublished. Ore grinding millstones are therefore often the only type of artefact serving to identify these types of mills. Since these artefacts are reported in many medieval mining districts (Benoît et al. 1996;Hrubý 2011;Minvielle Larousse et al. 2011b), the mills that drove them must have been widespread.
Since hydraulic ore mills have not, to date, been the subject of a specific publication, this paper is compelled to offer a detailed description of the different mill features brought to light at the different excavation campaigns water was spread throughout the area. Two large spoil heaps were downhill. Work related artefacts recovered in the area included mortars, pounders, millstones and a few iron objects (Bailly-Maître 2002a). Artefacts reflecting the miner's everyday life are also disseminated throughout the area, in particular in the rubbish dumps and in a domestic or administrative building. These artefacts include pottery, and remains of fauna, fruit, clothes, shoes, and other accessories.

Excavation of Sector B 121
The excavation of Sector B 121 (870 m2) (Fig. 2) was centred on the Font-Morelle spring toward the centre of the lower sector of the industrial area. Its eastern and western limits had been partially explored in previous archaeological campaigns (1980 to 2011). The exploration of the areas was intended to resolve three major issues: a) the organisation of the hydraulic system, b) confirmation of the presence of an ore grinding mill and c) exploitation of the Font-Morelle spring, the only source of sweet water on the plateau.
A three-year program was initiated in 2012 with fieldwork in the uphill zone, followed in 2013 by exploration of the central zone (the mill) and finalised in 2014 with work in the lower zone. The main results of the excavation are the following: Font-Morelle is a natural karstic spring located about 30 m north of the mill fed through a network of cracks and fissures. It has its origin at the Lac introduction of the geographical, chronological and functional context before describing the installation's main components: the hydraulic system and the mill-house. Hypotheses are then advanced as to how this industrial installation operated and its chronology before offering a series of notions regarding ore mills in general.

Ore grinding in an industrial quarter
Ore enrichment is a process that took place principally outside of the mine itself. Ore contained in a quartz-barium gangue had to undergo several manual and mechanical treatments, often carried out by means of hydraulic power. Old French texts most often indicate a process divided into three main stages (Bailly-Maître 2000; Mugueta Moreno 2004): 'crushing', 'grinding' and 'washing'. In practice, the separation of the different elements was progressive, implying that all types of ore did not necessarily follow identical processes.
Ore enrichment at Brandes was took place for the most part on the western edge of the settlement (Fig. 1). This industrial quarter, covering an area surpassing a hectare, was arranged around the Font-Morelle spring and a canal (C1) dug by the miners to direct water to the ore grinding and washing workshops. The workshops comprised at least two ore mills and many washing basins. The washing basins were both inside the buildings and outside in the open air. A network of underground conduits serving to steer, evacuate and drain

Mill
Blanc several kilometres to the north. The water also flowed through the mines and surged on the plateau. No anthropic feature designed to cap, guide or channel the water was observed at the mouth of the Spring.
Downslope from the spring, the upper area of the B 121 sector reveals two major phases of occupation. The first is characterised by the construction of a central terrace with an ore washing basin at is summit. The second is characterised by a heap of stones delimiting the edge of canal C1.
To the west, the study of the cross section of the spoil heap offered data regarding its content as well as the development of activities in the quarter. Far from being simply a waste dump, the zone served to process the mineral as evidenced by the presence of several washing features some of which contained deposits of sand resulting from grinding.
In addition, a large building with a stone floor unearthed to the east could have served an administrative or a storage function. Further downhill, another two spoil heaps were partially excavated with debris resulting from all of the different phases of the operational sequence of ore grinding and washing that took place at the workshops.

Stratigraphy and chronological phases
Sector B 121 presents four major chronological phases. The first, preceding the ore mill and probably stretching from the late 11th to the early 13th century, corresponds to the construction of the terrace located in the uphill zone. The second major phase is associated with the digging of canal C1, the installation of the ore mill and the mill's life-span from at least 1210/1211 to 1227. The third phase corresponds to a restructuring of the industrial area, the spoil heaps, and the abandonment of the mill in the second half of the 13th century. The final major phase is the progressive abandonment of the industrial activities. This last phase, initiated in the first half of the 14th century, culminated sometime in the second half of this century.
The stratigraphy observed during the excavation was mainly characterised by the abandonment phase. After the end of its operational life, canal C1 continued to "function" as a torrent until it was gradually backfilled with baryte waste and rocks of different size from the destruction of the different mining features. Although the canal was backfilled, the Font-Morelle spring continued to flow and deposit layers of sand in the area. Finally, when the spring's path was stabilised once again, the area was covered by a thin layer of peat.
The ancient features emerged progressively as each archaeological layer was uncovered. It must be noted that it was at times difficult to distinguish crude dry walling constructions from layers of destruction (Fig. 3). The mill's features appeared under the colluviums directly on the summit of the bedrock (Fig. 4).
The different forms of outcropping of the bedrock is essential to the understanding of the different features of the mill. To the west it surfaces in the form of a hard massive layer of gneiss while to the east it corresponds to a highly weathered Triassic dolomite formation.
Although no pre-medieval structures were identified in this area, it cannot be excluded that anthropic features preceding the mill were erased by erosion. Furthermore, the difference between natural fine hydraulic sands and gravels and human deposits is determined principally by the form of the grains: rounded edges for the natural grains and angular edges for those that are anthropic.

Canal (C1)
The mill was integrated into the pre-existent industrial hydraulic network. It was raised about 30 m downhill from the Font-Morelle spring along the course of canal C1. The earlier phases of the spring, before the mill, did not leave clear traces.
Yet what is important for the understanding of the mill is the course of the later contemporary phase of canal C1 that joined the spring supplying the force to drive the millstone.
It is noteworthy that the stratigraphic sequence of the canal at the level of the mill corresponded to deposits completely different from the backfills both upstream and downstream (Bailly-Maître and Minvielle Larousse, Site Report 2014). This indicates a constant flow of water through the head-race and through the spillway even when a part was directed through the undercroft to drive the wheel. The distinction described below between the two watercourses, the head-race and the spillway, is therefore artificial as they were originally both sections of canal C1. Yet this study maintains the traditional molinological designations of head-race and spillway for the sake of convenience.
Several trial trenches were sunk to observe the stratigraphy of Canal C1. The first, 50 m upstream of the mill, showed the canal to be 1 m wide and only 5 cm deep (Bailly-Maître et al., Site Report 2009). Twenty metres downhill, the canal's bed was 1.00 m to 50 cm wide and 80 cm deep (Bailly-Maître and Minvielle Larousse, Site Report 2011). In this area, part of the flow was diverted by two other channels to other workshops. Twelve meters downhill the canal joined the course of the Font-Morelle spring. At the level of the mill itself, the canal measured 1 m in width and about 1 m deep, consistent with the previous measurements. Then, at the level of the mill, the spillway became slightly narrower (about 65 cm wide) and attained a maximum depth of 65 cm.
The canal's bed is too irregular to estimate a rate of water flow, especially as the dimensions correspond to a maximum rate, and the amount of water available would have varied greatly depending on the seasons and the amount of rainfall. In any case, maintenance of the canal, due to all of its irregularities in the faults in the dolomite bedrock, would have been demanding.

The head-race
The head-race, the segment of Canal C1 to the north of the mill that steered water into the mill, traversed the dolomite bedrock along an east-west axis (Fig. 6). It is roughly 7.7 m in length and 80 cm wide. Taking account of the irregularities of the dolomite, this channel occupied a minimum area of 6.7 m 2 , and a depth between 1 m to the east and 60 cm to the west. Based on the average depth of 80 cm, its volume can be estimated at 4.9 m 3 , a volume that it could power the mill wheel. From the stratigraphic standpoint, the head-race was fi rst backfi lled with layers of fi ne sands and homogeneous clays, followed by several timbers. This layer was then capped by a deposit of larger materials comprising rolled baryte pebbles.
The head-race of this mill has a distinctive origin (Amouric 1984, 78-89) as it originally served as an open-air trench with inclined edges cut into the bedrock (7.7 m long and 0.3-1.5 m wide) to exploit a vein of argentiferous galena. The ground plan of the galena trench originally corresponded to 6.4 m 2 and its fl at base varied from 1 to 1.5 m in depth.
Few clues have survived as to the techniques applied to extract the galena. There is no trace, for example, of the use of fi re to weaken the mineral and there are only a few tool marks. A small working face preserved at its north-west end indicates two narrow, parallel trenches cut with a pick or chisel dividing the vein into three sections 10 cm wide. This cutting technique would have facilitated mineral extraction (Bailly-Maître 2002b, 80).
The vein was not fully exploited as 1-2 cm of galena remained along the north-east face. The western sector resulted in a face with a mineral still in place along a length of 1.1 m. What remains unclear is if the miners exploited the mineral explicitly in view of digging the mill's head-race or if the mill makers took advantage of a galena trench after its abandonment.
Along the northern edge of the head-race, toward the middle of the trench, was a spruce post measuring 40 cm long and 12 cm in diameter, wedged with stones in a crack of the rock. Dendrochronological analyses of the post indicate is was felled about 1210/1211 (Archéolabs, ARC 13/R4021D/1). This post suggest the presence of other wooden structures along the head-race's northern edge. The trench's southern edge is less regular and showed no traces of a timber.
Due to the irregular shape of the head-race corresponding to that of the original trench exploiting the galena vein, its maintenance must have been tedious. Moreover, as there was constantly 60 cm of water at a minimum, there was probably a high rate of deposition of fi ne particles that would have gradually backfi lled it.

The spillway
The spillway of a mill is an essential feature that regulates the rate of flow when a mill is at work or permits bypassing the water wheel when the mill is at rest. At Brandes it is to the west of the mill and oriented NE-SW (Fig. 7). It is about 4.4 m long and 65 cm wide, resulting in a surface of 2.9 m 2 . Its base attains the gneiss bedrock that is 60 cm higher than the head-race. This is an essential detail as it permitted a large volume of water to be collected at the end of the head race adjacent to the mill's wheel chamber.
From north to south, the spillway's eastern edge was a drystone wall oriented NE/SW, 1.66 m long and 1.12 m wide, built with medium-sized blocks (20-40 cm) and recycled millstones. Two abandoned millstones dressed with furrows and bearing striations of wear were placed vertically along its inner edge indicating that the spillway was at least 70 cm deep. The spillway's eastern edge then continued downslope along a bedrock platform oriented NE/SW occupying an area of 2.21 m 2 between the mill-house to the east and the spillway to the west. It is marked by an alignment 1.7 m long of a dozen medium-sized (20-30 cm) blocks. The third segment presents an elbow of 90° to the east, with 3 blocks 1.3 m long in contact with the western wall of the mill-house. A wooden post, felled in 1227-1228 (Archéolabs, ARC 14/R4095D), and wedged with small blocks in the platform, is about 15 cm in diameter and preserved over a length of 36 cm. This last group of features (under the water level at the time) is difficult to interpret. They probably correspond to elements of the base of the mill's timber superstructure.
The western edge of the spillway is formed by a drystone wall, 5 m long and 1.1 m wide oriented NE/SW. This wall contrasts with the other wall segments as it is massive and reinforced with timber. It occupies an area of 6.9 m 2 with an inclination of about 30 cm, and halts to the south just before a sort of step or tier nearly 80 cm high in the gneiss bedrock. At this point the spillway takes on the form of a classic construction with two parallel walls (only 1 to 3 rows are preserved). Several millstones are also included in this part of the construction. A whole runner stone is set to allow a spruce post 25 cm long and 10 cm in diameter to be inserted in its eye. Another post, a spruce 30 cm long and 12 cm in diameter, was wedged directly to the centre of the wall. It was presumably felled between 1210 and 1211 (Archéolabs, ARC 13/R4021D/1).
A sort of chute at the end of the spillway profited from a tier in the gneiss bedrock 90 cm higher on its eastern side that separated the canal into two distinct platforms. The course of the spillway, after the chute, continued 8.3 m downhill along a N-S axis, parallel yet separate from the tail-race. An alignment of three large discontinuous blocks totalling a length of about 1 m was arranged at the end of the spillway and served both to break the water flow and direct a part between it and the gneiss tier. Although crude, this feature was effective. Yet this contraption leads to the question of why the need to break the current? It may, in fact, have served to protect a washing feature downhill . As we have not observed any erosion of the washing structure's backfill, it seems that the blocks that broke the water flow served their function.

The tail-race
The tail-race is the canal serving to guide the water exiting the mill-house back into the original canal. The Brandes tail-race, only partially excavated, was deliberately dug by the miners for this purpose, as opposed to the head-race and spillway that profited from previously dug out features. Moreover, unlike the rest of the hydraulic system, the tail-race was deliberately backfilled in a second phase, after the abandonment of the mill. Its backfill consisted of a series of baryte waste deposits followed by a thick layer of rocks (Fig. 8).
The oldest backfills of the tail-race were identified in a trial trench. The deposit consisted of fine, sandyclay or stratified layers on an average 6 cm thick. These types of deposits are frequently observed in hydraulic features at Brandes. Although the trial trench was small and no characteristic artefacts were recovered, it is likely that the deposits were of hydromorphic origin resulting from operating the mill. Other anthropic backfills containing baryte debris were later deposited voluntarily throughout the length of the tail-race. Although the gravel and pebbles are mainly angular, some are rolled indicating they were transported by water.
How these deposits were formed and their function are sensitive issues. The first working hypotheses tended to see them a colluviums deriving from operation of the mill or other materials transported by water after the mill's abandonment. Yet this view was discarded as rolled elements were a minority and because the backfills, all homogeneous, are superimposed with well-defined limits. Therefore it is more likely that the deposits represent deliberate attempts to seal the tail-race. These backfills were ultimately capped by a thick layer of rocks, somewhat ordered, on the eastern border of the canal that served, on the one hand, to reinforce the canal to the west and contain a spoil heap to the east.
The precise course of the tail-race was not observed during the excavation as it was not possible, due to time constraints, to dismount all of the blocks in the area. It is assumed that the water from the mill exited the undercroft and ran to the south parallel to the spillway under the pile of rocks before joining the main canal. The water most likely followed a large fault in the dolomite bedrock (1.5 m wide at its top and 25 cm at its bottom and 80 cm deep,) that outcrops uphill from the mill (Fig. 9).
This natural conduit, whose axis coincides exactly with the supposed position of the tail-race, was partly deepened and widened by the miners as seen in the trial trench (Fig. 10). Yet the excavation of these features did not bring to light artefacts that could substantiate the tail-race's contemporaneity with the mill, the sunken features and the backfill.

The drystone walls
The mill-house has a roughly horseshoe shaped foundation to the south of the head-race and east of the spillway. Its foundation comprises three drystone walls (east, west and north) with an opening to the south (Fig. 11). The house was presumably organised with two floors: an upper floor containing the millstones where the grinding took place and an undercroft containing the waterwheel. Each of the walls of the mill is singular from the point of view of size and construction. Despite the differences, all three were probably raised at the same time.
The space where the grinding took place on the upper floor, oriented N-S, measured presumably 2.1 m in length. Its shape was not regular as along its northern edge it measured 1.9 m in width, expanding to 2 m at its girth, and 1.4 m at the southern end. The total surface of the grinding floor ranged from a minimum of 3.4 m 2 to a maximum of 5.2 m 2 .
The eastern wall measures 4.6 m long and 80 cm wide. It is the widest of the three. Besides small to medium-sized rocks (10-30 cm), it comprised, to the south, two large dolomite blocks about 1 m in length. Built directly on the bedrock in a narrow trench, its external face is irregular and merges with the surrounding blocks. The internal facing, by contrast, is much more organised and conserved to a height of 1.2 m. Toward its northern end it curves slightly inwardly (15 cm).
The western wall, separating the chamber of the waterwheel from the spillway, measures 1.8 m in length and 80 cm in width with a base consisting of four large blocks. Its rough aspect contrasts with that of its eastern counterpart. It too presents a slight inward curve to the north that combined with the eastern wall results in the horseshoe shape.
Finally, the northern wall is 1.2 m long, 30 cm wide and preserved at a height of 1.4 m. It delimited the house from the space reserved presumably for the flume.

The backfill of the mill-house
The backfill in the mill-house ranged from 1.2 and 1.4 m in depth. Its stratigraphy (from top to bottom) consists of four major deposits. The oldest is a layer of blocks and fragmented millstones in a heterogeneous, predominantly sandy, matrix. The size of the millstones in this level varies from small pieces a few centimetres long, to larger segments and halves (Fig. 12). This deposit capped a more homogeneous layer of gravel and baryte 5 to 20 cm thick containing many pieces of timber (see below) and a high concentration of millstone fragments (49). Finally, under the gravel and baryte, there were more fragments of wood and millstone flakes in a homogeneous grey to brown sandy layer. This layer did not contain blocks and only four millstone flakes, probably "infiltrations" from the upper units. This sandy layer rested on the top of the dolomite bedrock (Fig. 13).
The goal of analysing the mill-house stratigraphy was to determine, on the one hand, the nature of the deposits (deliberate demolition or natural colluviums), and if there are deposits associated with the mill's operation. The upper units containing the millstone fragments of different size in a sandy  matrix are clearly post-abandonment formed either by the progressive demolition of the structures or by a faster intentional anthropic backfill. Both are associated with colluviums deposited by water running through the canal. The lower deposits, by contrast, appear to be contemporary to the mill given the high number of small millstone flakes and their uniformity while the oldest sandy layer could correspond to ore grinding residue.

The undercroft
The base of the undercroft of the mill-house coincides with the summit of the dolomite bedrock. It presents an inclination of about 30 cm from its N-W corner to its S-E corner. In fact, a sort of channel is formed along its summit along the base of the eastern wall leading to the S-W. This feature, 2 m long and about 10 cm wide, then carries on for about 1 m along the base of the western wall before changing course and joining several faults in the dolomite oriented NW-SE (Fig. 14).
This asymmetry would have facilitated the evacuation of water by a channel drawn diagonally to the house through the faults in the dolomite serving as the tail-race.

Dolomite bedrock
Undercroft Dolomite block  The flume in a watermill equipped with a horizontal waterwheel is an inclined, tapered wooden feature that traverses the wall of the mill-house allowing the flow to be directed from the head-race into the waterwheel chamber and drive the wheel by means of a jet of water. In the case of Brandes, the cavity holding a hypothetical wooden flume measured about 2.1 m in length (N-S) and 1.4 m to 60 cm in width.
The flume would have been wedged diagonally in the space between a block bordering the head-race to the north and the northern wall of the undercroft (Fig. 15). This type of feature is evidenced by a horizontal wooden beam (Figs 16 and 17) fixed toward the base of the north wall serving as a sort of lintel above a quadrangular hole backfilled with baryte sand connecting the cavity to the waterwheel chamber. This hole would have been traversed by the nozzle of the flume.
The wooden beam has a central mortise suggesting the presence of a second beam projecting from it perpendicularly. and 20 cm in width and was backfilled with sand and rolled white baryte gravel. The hypothesis of a wooden flume is bolstered by the sediments observed during the excavation of the cavity between the undercroft and the head-race. From top to bottom they consist of an accumulation of blocks in a baryte sandy matrix similar to that at the base of the undercroft. This layer appears to correspond to deposits accumulated during operation of the mill. This notion is bolstered by the fact that it contained 73 millstone flakes.
The next layer consists of sand and blocks covering units of sand and rolled baryte gravel similar to the facies backfilling of the head-race. The final unit is the dolomite bedrock that shows an irregular shaped cutting about 1 m below the base of the walls measuring between 1 m to 30 cm wide and 2 m long. The cutting clearly connects the western end of the head-race to the base of the mill-house that is on an average about 55 cm downhill. This cutting profited from one of the dolomite faults, perpendicular to the exploitation of the vein, and appears to have been slightly extended.

Horizontal or vertical waterwheel?
Although the poor state of preservation of the Brandes mill does not allow determining beyond any doubt the means of traction, there are a number of features that suggest a horizontal waterwheel.
The first is the mill's floor plan. The undercroft's horseshoe shape and dimensions are compatible in width with a horizontal waterwheel. Furthermore, the inclination of the base of the undercroft could have served to guide the water from north to south through a fault in the dolomite bedrock to the west. This dissymmetry would not have been necessary in the case of a vertical water wheel. The general hydraulic system is also compatible with a horizontal water wheel. The northern wall was designed to take advantage of a fault in the dolomite that steered the water to the nozzle at the end of the flume to power a horizontal wheel. A flume can therefore also be inferred from the higher base of the adjacent spillway (in comparison to the base of the head-race) that allowed the retention of a great volume of water that could be directed either through the flume to the waterwheel or bypassed through the spillway during heavy rains or when the mill was at rest.
The hypothesis of a vertical wheel at Brandes is, in turn, hampered by two key elements. A vertical wheel, connected to the millstones by means of a complex gearing system designed to convert a vertical to a horizontal motion would have had to be located not in the undercroft but in the spillway. But since the base of the spillway at Brandes is higher than that of the head-race, the level of a horizontal driveshaft and gearing system connected to a vertical wheel would have been far too high in relation to the theoretical height of the floor of the mill-house.
What is more, reversing the location of the vertical wheel chamber and the spillway would have required the overflow of water, when the mill was not active, to flow through the "flume". But this second conduit, with only a small cavity at its base, would have been too narrow to cope with the large flow from both the spring and Canal C1.
Furthermore, a vertical waterwheel in the spillway would have had to be placed at the outset of the spillway, a location that would not apparently have been apt for a wheel driven by undershot.

A flume
A flume, in general, is a hollow wooden feature with an inverted, truncated pyramid shape, like an elongated mill hopper. A fine example was recently discovered during excavation of a mill of Kilbegly in Ireland (Jackman 2013, 5). The base of the flume can be prolonged by a nozzle. Although the size and shape of flumes can vary, their function remained the same: to direct a jet of water under pressure against the wheel.
In the case of Brandes, the theoretical wooden framework of the flume was set in a cutting carved into the dolomite bedrock. Yet, the direction of the cutting through the bedrock ending toward the south-eastern corner of the flume's cavity does not match the inclination of the undercroft. In fact, the stream of water would normally have been directed from the east yielding a clockwise horizontal wheel rotation. But the asymmetry of the bedrock is such that the water circulated diagonally from the northeast to the south-west resulting in a counterclockwise rotation of the wheel. This operation would therefore have required a short, angled spout at the end of the flume to direct the stream of water first along a north-south axis through the hole under the beam before veering to the south-west to make contact with the paddles of the waterwheel.

Remains of the waterwheel?
At the base of the undercroft, the successive stripping of the heterogeneous sandy deposits brought to light several pieces of wood resting at the summit of the bedrock, toward the base of the eastern wall, on the blocks and on a layer of baryte gravel mixed with pebbles (Fig. 18). Unfortunately the different pieces of wood are poorly preserved and their specifi c form and eventual tool marks are not discernible. Yet their spread is arranged in a tangential and radial scheme forming a sort of "circle" approximately 1.5 m in diameter. It therefore cannot be excluded that these pieces of wood are the remains of a horizontal waterwheel equipped with spoon-shaped blades around its central hub. A second option is that the pieces of wood correspond to the superstructure that supported the millstones.

The wooden superstructure
Based on the reconstruction of the initial position of the beam toward the base of the north wall, and taking into account the notch or slot cut into the wall, we can assume the presence of a similar second perpendicular beam projecting southwards from the central mortise (Fig. 19). Unfortunately its length is unknown as there is no visible mark cut into the dolomite bedrock on the opposite side of the undercroft.
It is diffi cult to establish a relation between this second hypothetical perpendicular beam and the horizontal wheel. The beam's level, in any case, higher than the base of the undercroft or the spout of the fl ume, excludes that it served as a support for the horizontal wheel. By contrast, its position suggests it could have served to stabilise the mill's vertical driveshaft that powered the millstones. Another option is that it did not stretch over the length of the undercroft, excluding a relation with the waterwheel, but in some way forming part of the mechanism supporting the millstones.
The mill-house's superstructure comprised at least three wooden posts. The fi rst, PO 121-258, is toward its south-west corner while the two others ) are on either side of the spillway's western wall. Post 121-197 was probably integrated into an alignment that was parallel, perpendicular (or both) to the western wall. In the fi rst case, two other posts along the wall's edge are missing. In the second case, the alignment could correspond to a gap at the southern end of the spillway's eastern edge. But here, too, an additional theoretical post, or at least a notch on the wall, is missing. Post 121-202 could also be part of an alignment parallel felled in 1227/1228 AD. Finally, a piece of wood recovered in the backfill of the head-race, hence most likely dating to the mill's abandonment, was felled after 1223, possibly in 1228. Yet this second date must be considered with caution as the wood is in secondary position and many years could have elapsed before it found its way into the head-race.
It is therefore certain that the ore mill of Brandes was in operation in the first half of the 13th century. This is bolstered by the 13th century date attributed to the metal working area upstream of sector B 102 linked to the mill by means of canal C1.
In spite of a clear date for the mill's construction, there is, in turn, little evidence of its abandonment. The dendrochronological analysis corresponding to repairs in 1227/1228 suggests that the mill operated for at least 17 years. Yet the date of the repairs does not constitute an terminus ante quem and the mill could have seen use beyond that time frame.

An industrial mill
The layout of the mill was designed to concentrate all of its features in the smallest possible space (Fig. 20). Taking into account the head-race, the tail-race, the spillway and the mill-house, the mill occupied a surface of 62 m2. Its total length from the northern end of the head-race to the southern end of the tail-race was about 20 m. The width of the mill-house was 5.5 m and the length of the mill-house, including the flume, was 4.6 m.

Construction and architecture
The mill's construction was clearly defined by the outcropping of the bedrock as it profited from the natural features inherent to the junction of the masses of dolomite and gneiss. The mill-house, for example, was set on the dolomite so as to take advantage of the faults running east-west for the head-race and the north-south faults for the flume cavity. The tail-race also profited of a north-south fault in the dolomite to evacuate the water. The spillway, in turn, was built on the gneiss and benefited from a raised section of the rock to separate it from the tail-race.
In addition to the opportunism in the choice of the location, the builders of the mill applied a very rudimentary construction technique using rough, unworked blocks of different size. This indicates that there was no regular supply of building materials from a specific quarry or of a specific type of rock. To gain in time and expense, the mill was in fact built with readily available local surface materials. This also explains the reuse of many millstone fragments as construction material. In addition, many of the dolomite blocks may have come from the spoil resulting from the cutting the trench of the head-race, the levelling the bedrock under the future mill-house or the digging out the mill's wheel-chamber.
to the wall. But here, once again, the theoretical posts to the north and south are missing. It could also be part into a perpendicular alignment and would, in this case, be linked to post 121-258.
In any case, the few posts that have survived, including post 121-156 to the north-east of the head-race, do not offer enough data to securely reconstruct the mill-house's timber superstructure.

The flow of water
While the surface of the dolomite bedrock suffered from decalcification and karstification due to prolonged contact with moisture, the harder gneiss bedrock remained largely unaffected except for a rounding and smoothing of its edges visible in the spillway where it was subject to a regular flow.
The flow of water also had an effect on a millstone (OBJ 2014-163) placed vertically in the eastern wall of the spillway with its grinding surface facing the water (Fig. 19). The upper limit of the wear on the stone, 30-40 cm above its base, indicates the normal level of the water running through the spillway. Similarly, the rocks of the lower rows of wall MR 121-171 are greatly weathered as opposed to the upper layers of the same wall where the blocks retained their original angularity. These features indicate a regular and strong current of water.

The millstones
A large number of elements of millstones (125 fragments and 309 flakes) were found in the mill and its immediate surroundings. Their average diameter is estimated at 110 cm. Among the 125 fragments, there are four that are practically whole, five halves, 13 segments and many other fragments of different sizes. The largest concentration of fragments and flakes was in the mill-house (44 fragments and 220 flakes). Some fragments were scattered in either the backfills of the spillway and the tail-race while others (19) were re-cycled as building material in the mill's structures. This material is currently under study for a future publication (Minvielle Larousse, in press).

The evolution of the mill
The reuse of millstone fragments as construction material, some at the base of certain structures, indicates that the excavated mill was preceded by at least one other mill raised either in the same spot or nearby. The construction of the excavated mill, based on dendrochronological analyses of at least two of the posts, can be precisely dated to 1210-1211 AD. Moreover, post 121-197 was still green indicating it was raised shortly after it was felled. The date of the felling of the beam serving to support part of the wall of the flume, in turn, came sometime after 1201, a range that is not inconsistent with a construction in 1210.
Furthermore, the wooden superstructure of the mill was revamped or extended with timber   While the mill of Brandes used stones for its foundations, wood served for the wheel and gearing mechanisms and to support the superstructure. There is no indication of the use of iron in the construction. This absence appears to be deliberate as smithies are common to Brandes. The hypothetical elevation of the Brandes mill therefore differs from the ore mill represented in the 16th century engraving by Georgius Agricola (Fig. 21) (Agricola 1950, 294) housed under what is a structure raised entirely of wood.
The Brandes mills therefore may have been simply an open platform as grinding ore, contrary to grinding cereals, for example, would not have required protection from the elements.

The mill mechanisms
In general, the horizontal waterwheel places the Brandes mill in a broad technical context. Horizontal wheels, one of the simplest driving mechanisms, have been regarded in mill literature as primitive (Bloch 1935) or as the ancestor of the vertical wheel (Braudel 1993, 400). Contrary to this pejorative view, it has in fact been demonstrated that the horizontal wheel existed since the origins of hydraulic milling, was contemporary to the vertical wheel (Comet 1992, 439) and was bound to specific geographical areas (Benoît 2014).
Recent field work suggests that vertical wheels during the Early Middle Ages coincide with regions that were under Roman control, whereas horizontal wheels were restrained to the "barbarian" regions, outside Romanised spheres (Benoît 2014). However there are exceptions to this rule.
In Central Europe in the Middle Ages, the horizontal wheel was in fact widespread both in Provence and the Dauphiné despite a limited number of historiographic records (Amouric 1984, 130). The larger number of written accounts regarding verticals wheels in the Dauphiné is probably due to their exceptionality when compared to their horizontal counterparts. For example, the Huez flour mills (Combe Basse), mentioned in records as early as the 14th century (Minvielle Larousse 2009, 130-132), are known to have been driven with horizontal wheels as late as the 19th century. The mill of Brandes, therefore, follows in the wake of this tradition.

A functional mechanism
Since the blocks used to build the mill were not fashioned, not even roughly squared off, we can assume the mill was constructed hastily without concern for its appearance. The early 13th century is a particularly active phase of mining at Brandes. It is therefore logical that additional installations were added to treat the ore when the quantity mined exceeded its processing capacity. An analogous situation is recorded at the Mine of Orzals (France, Aveyron) in the second half of the 13th century when the Count of Poitiers, desiring to immediately increase ore processing, sent a number of letters to his officers demanding that they rapidly construct all types of mills (water, animal, wind) to increase production (Dossat 1975, 91). Moreover, the materials used to construction the Brandes mill suggests that there was no intent in raising an ostentatious mill, as was the case at times of contemporary grain mills. The aim of this ore mill was strictly functional, tied to the necessity of boosting production.

The ore mill in the mining operational sequence
This mill was not the only 13th-century mill at Brandes. Besides traces of an earlier mill in the immediate whereabouts, there was at least one other mill further upstream on the C1 Canal (Minvielle Larousse et al. 2011a, 474-77). Yet the number of mills was very low compared to the quantity of crushing workshops and washing basins. In fact, water mills were not essential or used systematically in the operational sequence. In any case, two concentrations of sand deposits associated with millstone flakes were found in washing basins to the west indicating that they served to process materials ground in the mills. Yet the coexistence of sand with millstone fragments was identified in only two of the many washing basins. This bolsters the notion that mills at Brandes played a minor role in the ore enrichment process.
Regarding the organisation of the working process, grinding, contrary to crushing (and possibly washing), required collective equipment implying a specific type of management and taxation. No written text has survived that throws light on this question at Brandes. Nevertheless, ore grinding in other regions, like grain milling, was integrated into the seigneurial economy (Belmon 2003, 271-273).
This leads to the question of whether the leaders of society prompted the passage from manual to hydraulic grinding. For the period of Antiquity, in fact, no hydraulic ore mill is currently known (Pulou et al. 1997) in spite of a wide dissemination of watermill technology (Brun and Borréani 1998, 307-318). Therefore, did medieval miners have needs beyond that of their earlier Roman counterparts that required the systematic use hydraulic power for ore grinding? Yet since the constraints due to the type of ore and the will to optimise production were probably identical in Medieval and Roman times, the need of hydraulic power to drive the ore mills was therefore probably an imported idea.

Conclusion
Ore grinding at Brandes up to recently was the only stage of the ore enrichment process that remained in the shadows. The results of this excavation campaign, in conjunction with the study of the millstones, offers a broader view of the ore enrichment process, from the phase of extraction to that of working the metal. Moreover, this mill is an addition to the ever growing list of excavated medieval hydraulic works and another example of the use of water power in medieval industry. Data gleaned from archaeological work at times raise more questions than they answer, and the problems of interpreting certain features are much more complex than initially considered. Thus, the excavation of the Brandes ore mill is another element in the growing discussion of the process of innovation and mechanisation of mining in Antiquity and the Middle Ages.


Assessing Factors Influencing Investors’ Preference Towards Municipal Bond in Bangladesh

There has been much interest among the researchers to find out future prospective of municipal bond in Bangladesh. Especially as Bangladesh has become a developing country, the necessity of an efficient bond market has raised the concern. However, people are more interested in the money market. This paper has tried to find out the impact of possible internal and external factors, which can influence a municipal bond investment decision. With the help of secondary data, it has been found that fundamental factors such as yield to maturity can influence the investors’ decision whereas; external environment like the political condition of the country doesn’t play any impact here

Introduction
The financial market is the main pillar of economic growth for any country. It ensures the flow of fund from the surplus group to the deficit. It comprises of both capital market and money market. Capital market is standing for long term financing, while money market represents short term financing. The bond market is a part of this capital market.
Bangladesh bond market plays a very small role in the current economy. This market is mainly dominating by treasury debt securities. As of today, only a few listed corporate bonds and few unlisted are trading in the market (Uddin, J. and Sultana, N. 2013). Though the presence of corporate bond can be noticeable still the existence of municipal bond is invisible. Almost 70% of the domestic savings are kept in the form of bank deposits, while only 30% are debt market investments which are entirely dominated by government instruments (Jahur, S.M. & Quadir, N. 2010).
The main objective of this paper is to contribute to the development of an effective government bond market. As a municipal bond is one of the important instruments for an active government bond market, the paper aims to know the potential investors' preferences regarding investment decision on municipal bonds. It aims to identify whether fundamental features of bond can affect the bond investment decision. Moreover, the paper also aims to identify the external environment's influence on the investors' bond investment decision.

Bond vs. Municipal Bond
A bond is a fixed interest financial asset issued by governments, companies, banks, public utilities, and other large entities. Bonds pay the bearer a fixed amount on a specified end date (Shubik, 1999). There are different types of bonds, among them, one is municipal bond. It can be issued by local government, cities, countries, etc. and this is a type of loan investors provides to the government (Dove, J. 2016). Generally, municipal bonds offer a higher level of the income tax bracket and a higher level of the interest rate. As a result, this financial instrument is considered as a less risky and safest investment instrument (Schultz, P. 2012).

Contribution of municipal Bond in Different Countries
It is a common practice for first world countries, to issue municipal bonds for arranging funds in order to infrastructure development. In the United States, bonds issued from government or government agencies are used to finance a wide range of public projects such as ports, airports, highways, sewage, hospitals, and colleges. (Suk Huyn, 2008). Again the Polish legislature made amendments to the Polish Law on Bonds in 2001 to allow certain entities to issue revenue bonds to facilitate the financing of public services. It was expected that the introduction of an innovative financing instrument would enable a new class of investors to finance infrastructure for the first time in Poland. (Suk Huyn, 2008).
For the last fifteen years, municipal borrowing in Canada is on the rise (Fieracapital.com. 2019). Canada's municipal bond market is dominated by two different types of obligation. This market has increased significantly from 2.8 percent in 2008 to 7 percent in 2013, which reflects municipalities' favorable credit conditions (Hanniman, K. 2015).

Bond Market in Bangladesh
In Bangladesh, it is a common practice to arrange a loan from donors like the World Bank, ADB, etc. Such loans contribute to the development but at the same time, it increases the country's dependency over others. A country should use such an option on a limited scale but they should not rely on it all the time. Issuing bond can be considered as a great alternative to arrange finance (Islam, M. and Jahan, S. 2012). There is no need to choose a single instrument between bond and loan as the right way to handle local government credit. Many countries simultaneously use bank lending to municipalities and local bond issuance (Peterson, 2006). The policy rationale, however, justifies emphasizing the development of local bond markets (Alam et al. 2016). The public monitoring and public disclosure required for efficient bond market operation are consistent with greater transparency for all public financial transactions (Cuny, C. 2018). Currently in Bangladesh municipal bond hasn't been introduced. At the present time in Bangladesh, most of the companies or individuals prefer to take a loan or to keep deposit instead of investing in bonds. One of the main reasons is people are mostly aware of such options; they never think about managing the portfolio to avoid risk. Moreover, the interest rate of all saving instruments has increased to make them more attractive to investors. Such steps are working as barriers for the efficient bond market (Guarantco.com, 2019).
During 2013, when Bangladesh was going through a political crisis; banks & other financial institutions suffered from excess liquidity problem. Bangladesh Bank solved this situation by selling more T-Bills and T-Bonds. Bangladesh has evidence of government bond's contribution to solving the economic crisis, which indicates the availability of municipal bond can bring the blessing of economic prosperity as well (Chandra Das, B. 2014).

External Environment for bond investment
Importance of certain external factors on the investment decision has been analyzed in different papers. Social, political, legal, economical factors can be considered as External environments for bond investment (Marszałek, J. 2015). Bialowolski, P. and Bialowolska, D. W. (2013) have highlighted some of the external factors' influence in investment decision in Poland such as legal environment, macroeconomic factors, etc. According to Musazi et al., (2006) their research on banking industry shows tax law changes has an impact on the interest income from the municipal bond. The research conducted over 73 banks in the USA, as an investor will earn fewer amounts, their interest in municipal bond also declines. Besides these, it has also been found that the introduction of the euro currency in the European Union has influenced the bond market (Philippas, D. and Siriopoulos, C. 2014).

Fundamental features of bond
Some of the fundamental features of a bond are maturity, interest rate, tax bracket, liquidity, etc. (Park, S. 1995). Changes in these features can impact in the bond market, which has been studied in different parts of the world (Levine, H. and Greaves, P. 2013). According to Chopin, M. (1998) in the USA, changes in the maturity structure of other investments options, such as treasury borrowing can impact on the rate of return and municipal debt market.
For smooth operation, an important bond market should operate well. This indicates the availability of both efficiency and liquidity (Jong, M. 2013). Efficiency indicates bond prices incorporate all available information. It facilitates investors to invest more in the bond market and liquidity implies the reduction of bond market's transactions costs for investors (Chtourou, H. 2015).
Various researchers across the world have worked to analysis the bond market and its contribution to the economy but in Bangladesh, it has been always ignored to analyze investors' perspective while taking an investment decision. Moreover, most studies in Bangladesh focuses on the bond market while ignoring municipal bond. To cover this knowledge gap, the following null hypotheses have been developed based on the literature review:

Methodologies
To conduct the hypotheses primary data has been collected by conducting a survey. A survey has been conducted over 270 share market investors from different investment houses. As the population size is very high it is widely acceptable to prepare a sampling frame and take probability sampling (simple, stratified, or systematic) (Thompson, 2002). As taking probability sampling from such a big population is very expensive and time-consuming, non-probability sampling has been applied here. The sampling is done by using the quota sampling method. The quotas are selected based on three different points.
 Age of consumer  Earning level of consumer  Investment level of consumer In order to overcome the limitation of non-probability sampling, this study is highly concerned about the proper representation of the real population. So cross matching is done to make sure proper representation and sampling is done under 9 different quotas. At least 30 respondents have been collected under each quota. samples As most of the findings are qualitative, measurement is done based on the statistical relations between the variables. The Likert scale was used here to rank the preference of the investors and to present the analysis in a more acceptable and logical manner. Consumers' qualitative characteristics (dependent variable) such as age, earning level, income level has compared with the other factors (independent variables) by cross-tabulation, which also includes the Chi-Square tests. That will give a proper figure of confidence about the reliability of this study. For conducting cross-tabulation, linear regression, frequency analysis Microsoft Excel, SPSS 24 has been used.

Data Analysis
If the investors get an opportunity to invest in a Government bond or in other words a municipal bond, preference for investment varies depending on the features of bond. The percentage distribution of different fundamental preference is presented in Table 2. In this study, the priority for different features was tried to view from different perspectives. With the help of the Likert scale, it is tried to identify the preference level as well. 63.2% people prefer to invest in long term bond, here it needs to be mentioned that as bonds are part of the capital market, which is standing for long term investment, people's preference indicates that they are interested in investing by knowing the right purpose of the bond.

Test of Hypothesis 1
For testing the hypothesis, regression has been run; the significance level has considered 10% (.01). It means if the significance level is more the 10% then the reliability of the test can be ignored.

800(Yield to maturity)
As from the table, it can be found that β ≠ 0, so null hypothesis is rejected. It can be concluded as the investment amount is influenced by different fundamental factors of the bond like, life of long term bond, yield to maturity and active secondary market.

Outcome of Hypothesis1
By analyzing the regression, for hypothesis 1; it can be stated that the null hypothesis is nullified. It means investment decision is going to be influenced by different fundamental factors of the bond. Besides this, from the preference table, it can be found that more than 60% of people are considering different fundamental factors of bond as a major issue while making the investment decision. By considering all this information, it can be strongly stated that different fundamental factors of bond are important to establish the government bond/ municipal bond market.
The implication of this analysis is if the government decides to go for bond issuance for infrastructure development then they need to offer an attractive yield to maturity and have to establish an efficient secondary market as well. As there are other investment options in the market, so to attract the investors it is important to offer a high yield. Again an active secondary market ensures the liquidity of bonds, which plays a great role to attract the investors. It needs to be mentioned here that recently the government has launched a secondary market for bonds. So, at the present time, there are opportunities for the government to go for bond issuance for public infrastructure development.

Test of Hypothesis 2
To test this hypothesis significance level has been considered as 10% as well.

Outcome of Hypothesis 2
After completing the above regressions, 2 nd hypothesis can be concluded as the null hypothesis can't be rejected. It means bond investment decision is not influenced by the external environment. As the regression has very high significance, this has established the null hypothesis.
The outcome of this hypothesis can be explained as, if the present government goes to offer bond for infrastructure development, current anti-corruption system is not going to work as a boundary for this. As the country has gone through the election last year and people are predicting to have a stable political condition, this factor is not influencing the investors' decision.

Conclusion &Future Scope
The bond market plays an important role in the smooth running of a country's economy. A municipal bond is a vital element of this pillar. As Bangladesh has started its journey to be a developing country, this is the crucial time to establish an effective municipal bond market. This sector has a lot of opportunities to contribute to the economy. From the above study, it can be clearly identified that attractive fundamental features of a municipal bond can motivate investors to participate in this market and current external environment will not create any obstacle in the establishment of an efficient bond market.
Researchers have numerous opportunities for conducting in-depth study in this sector. Before introducing municipal bond, it is important to conduct research to know details about investors' knowledge level regarding the municipal bond market. Moreover, further research needs to be done to find out the impact of tax rebate in municipal bond preference.