Pepper Wreck: 2000 Field Season
|Line 306:||Line 306:|
Revision as of 20:23, 22 November 2010
The fourth and final field season on the Pepper wreck finished in August 2000, at least in terms of the field work. It was sponsored by the Instituto Português de Arqueologia (IPA), through its underwater archaeology department, the Centro Nacional de Arqueologia Náutica e Subaquática (CNANS), and the INA. In this last season we were also sponsored by MARCASCAIS, the company that manages the new marina of Cascais, where our boats were stationed. This wreck, thought to be the remains of an early 17th century Portuguese East Indiaman was discovered in 1994.
Excavation began in 1996 and yielded a collection of thousands of artifacts, as well as part of the hull structure. Objectives in 2000 were to complete the recording of the remaining hull timbers to permit study, analysis, and partial reconstruction of the hull.
Part of the timbers were raised, and part left in situ under a layer of sand bags, protected from the strong dynamics of the sea. A new area was inspected, a scarce 100 m from the SJB2 site, where timber remains had been spotted last winter by our longtime collaborator and close friend Carlos Martins. A very experienced diver, Carlos Martins has found most of the sites around São Julião da Barra, and has been our best guide to archaeological sites on that rough bottom. A layer of sand no less than 2 m thick, as well as a strong current, prevented us from reaching its level in the three trial trenches that we opened.
As it always happens in underwater archaeology, the conservation work and analysis of the artifacts will go on for a long time, as well as the reconstruction of the hull. In fact, the hull has shown to be the most important of the artifacts on this site. Although it consists of a very small portion of the bottom of the ship, its timbers, with construction marks engraved on their faces, speak volumes.
The wreck site is located within an area that might be termed an archaeological complex, a relatively small stretch of sea bottom containing several shipwrecks.
The strong dynamics of the sea and annual shift of sediments have combined to mix the artifacts of several shipwrecks, making this site at once an interesting and rich ship graveyard, but also a true nightmare for archaeologists, since the material culture represented in the collection of artifacts from this site encompasses a period of over 350 years. According to a database generated by CNANS, many wrecks were lost at the mouth of the Tagus, a general designation that encompasses a very extensive area. Fortunately, the area of the fortress of São Julião da Barra is small and well defined and having such a precise toponymy, most vessels lost here are specifically referred to in official documents as being lost off the fort, rather than at another, less precise designation.
The records often correspond with and explain the provenience of artifacts retrieved or located near São Julião da Barra. These known wrecks date from the late 16th century to the middle 20th century (Table I).
|1587||San Juan Baptista||Lisbon||Near the fortress|
|1606||Nossa Senhora dos Martires||Cochin, India||Under the walls of the fortress|
|1625||Sao Francisco Xavier||Cochin, India||Presumably near, south of the fortress|
|1733||Union||St. Malo, France||Near the fortress|
|1753||Dutch vessel||Presumably near, east of the fortress|
|1802||English vessel||Near the fortress|
|WWI||Maria Eduarda||Viana, Portugal||Presumably near, west of the fortress|
|1966||Santa Mafalda||Near the fortress|
The first challenge of this study has been the identification of the Pepper wreck, or SJB2 as it is designated in the map of the complex. One important clue was a thin layer of peppercorns, covering the hull timbers and extending over a very large area which contained a very homogeneous collection of artifacts dating from the late 16th century and early 17th century. The Chinese, Japanese, and Burmese pottery found in the pepper layer can be dated from the late 16th and early 17th centuries, and bears a great resemblance to the collection of the Manila galleon San Diego, wrecked in the Philippines in 1600. The porcelains, from the Wan-Li period, date from the 1590s and 1600s. An astrolabe found within the site bears the date of 1605, establishing the earliest date for the wreck.
The evidence we have uncovered points to one particular vessel, the Nossa Senhora dos Mártires, a ship presumably built in Lisbon and employed in the Carreira da India, the lengthy voyage between Goa and Lisbon. Mártires wrecked off São Julião da Barra in 1606 on a return voyage from Cochim on the Malabar coast of India. The identity of the wreck as the Mártires is reinforced by the presence of large quantities of peppercorns, indicating a bulk cargo of pepper, and therefore an Asian origin for the trip of the wrecked vessel. A study of the woods utilized - cork oak (Quercus suber) and umbrella pine (Pinus pinea) - and the scantling dimensions leave no doubt that this is a Portuguese built hull (Tables II and III).
|Unit||16th/17th c. Equivalent||SI Equivalent|
|Palmo de vara||1/7 of a rumo||22 cm.|
|Palmo de goa||1/6 of a rumo||25.67 cm.|
|Vara||5 palmos de vara||1.10 m.|
|Goa||3 palmos de goa||77 cm.|
|Rumo||2 goas, 6 palmos de goa, or 7 palmos de vara||1.54 m.|
|Polegada comum||1/8 of a palmo de vara||2.75 cm.|
|Polegada de goa||1 palmo de goa - 1 palmo de vara||3.67 cm.|
|Timber||Wood||Sided Dimensions||Molded Dimensions|
|Keel||Cork oak||25 cm.||Not preserved|
|Floors||Cork oak||23-25 cm.||23-24 cm.|
|Futtocks||Cork oak||21-25 cm.||11 cm.|
|Planking||Umbrella pine||20-35 cm.||11 cm.|
|Apron||Cork oak||38 cm.||25 cm.|
|Room-and-space||46.2 cm. avg.|
During the 16th and 17th centuries a small fleet would leave Lisbon for India almost every year, making the India route the longest regular route of its time. The ships were designed and built specifically to sustain a six-month-long trip. These vessels had to offer enough space for their crew and passengers, together with their victuals, and leave enough free space for the large amounts of merchandise brought back on the return trip. Their main cargo - peppercorns - was a very light commodity to store in the holds, especially if these vessels were to carry heavy artillery on the upper decks.
Therefore, a large amount of ballast had to be added, creating an even greater demand for space in the holds. All things considered, it seems incredible that the average late 16th century India route nau had a keel length of less than 30 m (100 ft.).
The illustrations of these early 17th century India route naus are scarce and generally inaccurate, but we are lucky to have a few late 16th and early 17th century texts that discuss the conception of these ships. Four texts are especially important and deserve mention here, since I have drawn much from them in the reconstruction of the hull remains.
The first is known as the Livro da Fabrica das Naus, written in Portuguese by a priest and adventurer named Fernando Oliveira around 1580, being a translation of a previous work of his, Ars Nautica, written in Latin, whose manuscript is in the University of Leiden, and has been dated to around 1570.
The second is an anonymous list of the timbers necessary to build a three-decked, 600-ton nau for the India route part of a codex of Lisbon's National Library, dating from the 1590s, known as the Livro Náutico.
The third is a manuscript titled Livro Primeiro de Arquitectura Naval, and consists of an incomplete recipe for the building of a four decked nau written around 1610 by João Baptista Lavanha, engineer of the kingdom, mathematician and author many other books. The fourth is perhaps the most interesting and elusive of them all, since the author is virtually unknown in spite of the magnificent self-portrait and signature with which he opens his book. It is called Livro de Traças de Carpintaria, dated 1616, and signed by a Manoel Fernandez, shipwright.
Based on the common characteristics mentioned in these texts we have a fair idea of how these vessels were designed and built. However, when it comes to details, we have few certainties, many doubts, and a great deal of ignorance about the shipwright's methods, techniques, and practices. This is why archaeology is such an important discipline.
The remains of the SJB2 hull consisted solely of a portion of the keel, eleven frames, an apron, and an area of planking covering around 12 by 7 meters. However, the marks of the iron spikes with which the planks were nailed to the frames showed a clear pattern, and helped us to determine the position of another fourteen frames.
Ilustration from Manoel Fernandez' Livro de Traças de Carpintaria.
Before starting the reconstruction of the hull I have performed a series of checks on the accuracy of the 1997 site drawing, comparing the measurements of the timbers raised in 1999 and 2000 with its equivalent in the scale 1/10 plan made during the 1996/97 field season, by reducing a large number of 1/1 drawings made over plexiglas slates on the bottom. I found a discrepancy of 5 cm in the longitudinal direction, over a distance of 12 m, representing an error of less than 0.5%, and of 3 cm in the transverse direction, representing again less than 0.5% error in the overall measures. The position of each spike hole in the planking was checked on the north half of the wreck by an independent team, but this was only partially done on the southern half, leaving a few - not very important - doubts here and there.
The presumed positions of the above-mentioned fourteen frames marked on the planking were strongly reinforced by the existence of a number of interesting surmarks on the floors and futtocks. Once analyzed, the positions and meanings of these marks give us a very clear picture of the principles that guided the conception and construction of this vessel.
As mentioned above, eleven contiguous floor timbers were preserved over the keel, growing in their molded dimensions from the north to the south, in the direction of the bow. They showed four types of surmarks (Table IV): a sequential numbering in roman numerals; a series of marks that seem to have no precise meaning, presumably resulting from scratching during the construction process; a series of vertical lines, marking the edges - in Portuguese astilhas - and the axis of the keel; and a series of lines marking other construction features.
Of this last group, four vertical lines are clearly placed on what I believe to be the turn of the bilge points, and another three deserve a closer look, since their meaning is not clear at this point.
Two are also vertical marks on the aft face of floor timbers C2 and C3, and the third is a line on the base of floor C3.
|Floor Number||Marks With No Obvious Meaning||Keel||Lines|
|C2||'X'||Curved groove on PS||Axis & Edges||63 cm. to PS|
|C3||'VIIII'2||Curved groove on PS||159 cm. to PS, 169 cm. to SB (vertical) & 108 cm. (on the base)|
|C4||189 cm. to SB4|
|C5||193 cm. to SB4|
|C6||197 cm. to SB4|
|C7||'V'3||200 cm. to SB4|
|C9||'III'||Axis & Edges|
|C10||Axis & SB Edge|
1. Positions: all marks on the aft face of the timbers, except the one on the base of C3; PS - Port Side, SB - Starboard
4. Presumed to mark the turn of the bilge
All four texts mentioned above describe the process of building the hull that is generally known as skeleton-first, or frame-based, as it is perhaps more accurate to say. In this method - typical from the Mediterranean tradition and already many centuries old in the 16th century - the central section of the hull was defined through a certain number of pre-designed and pre-assembled frames that were mounted over the keel. The widest frame (or frames) of this group was generally placed in the center and called midship frame(s), or master frame(s). The last of these pre-designed frames, fore and aft, were called tail frames. The fore and aft 'ends' of the hull, called delgados in Portuguese, were defined by a series of ribbands that ran from post to post, and over these central, pre-designed frames, to ensure that the planking would have smooth runs and would not endure unnecessary stresses during its lifetime. At the same time this system ensured that the bow and stern would have beautiful and fair shapes, cutting the water easily, and avoiding any turbulence around the rudder. The remaining frames may have been shaped and fitted only after all the ribbands were set in place. In this system of construction shipwrights did not depend on drawings to define the shape of the pre-designed frames. Their shapes were obtained from a rectangular mould and set of gauges, called graminhos, which determined the rising of the bottom and its narrowing, from a maximum width at the flat midship frame to the 'V' shaped minimum width and maximum rise at the tail frames.
Following a very simple procedure, the total rising or narrowing was divided by the number of floor timbers over which it was to be distributed by a simple algorithm called besta (cross-bow) in Portuguese, the equivalent of the Italian mezzaluna. This algorithm was therefore utilized to build a gauge, called graminho, with the full scale measures to be added or subtracted from the main mold of the midship floor.
When I measured the molded dimensions of the floors over the keel, and plotted their heights together with their respective sequential numbers, I have obtained a series of values that followed very closely the rising of the bottom recommended in Oliveira's Livro da Fabrica das Naus (Table V) for a nau of 18 rumos of keel.
|Floor||Number||Height Over the Keel||Theoretical Vales After Oliveira|
|C10||II||31 cm.||26.4 cm.|
|C9||III||25 cm.||27.2 cm.|
|C8||IIII||27 cm.||28.5 cm.|
|C7||V||36 cm.||30.0 cm.|
|C6||VI||31 cm.||31.9 cm.|
|C5||VII||35 cm.||34.0 cm.|
|C4||VIII||37 cm.||36.5 cm.|
|C3||VIIII||39 cm.||39.2 cm.|
|C2||X||42 cm.||42.1 cm.|
|C1||XI||46 cm.||45.4 cm.|
According to Father Oliveira, an India route nau must have 18 rumos of keel, three midship frames, and 18 pre-designed frames before and abaft these three master frames. The total rising of the bottom should be the equivalent to one room-and-space to the bow, and one and a half room-and-space to the stern. I moved on to varying the number of pre-designed frames, as well as the value of the rising, since the Livro Náutico determined that an India nau should have one single master frame, and 17 pre-designed frames before and abaft of the master frame, and the rising being three palmos de goa - one rumo equaled six palmos de goa - to the stern (the rising in the direction of the bow is not mentioned). Lavanha's Livro Primeiro indicates only one master frame and five pre-designed frames fore and aft, but mentions an old method with 15 pre-designed frames to each side of a single master frame. Fernandez's Livro de Traças indicates also 15 pre-designed frames to each side of three master frames.
After considering all sets of values I could find, it still looked very much like Oliveira's pattern was the recipe utilized in the conception of the bottom of what we presume to be the nau Mártires. It must be stressed here that the spike marks on the northern planking show clearly a set of three floors placed together, to which should be assigned the number zero, if the numbering order observed in the preserved ones is considered.
Following this line of reasoning, I then tried to relate some of the vertical marks observed on the floors with a few theoretical curves drawn from Oliveira's book for the narrowing of the bottom. Again, if considering three master frames, as seems to have been the case, four consecutive marks match within 1 cm the expected values for the turn of the bilge (Table VI), when a flat of 2 2/3 rumos (4.11 m) and a total narrowing of 1/6 of the flat along the pre-designed 18 frames are considered.
Both these values of the flat of the midship frames, or plão, as it was designated in Portuguese, and the total narrowing, are perfectly within the values indicated by Father Fernando Oliveira. For a length of keel of 18 rumos (27.72 m), the stem should spring forward 6 rumos (9.24 m) and the sternpost rake abaft 1 palmo for each 4 or 4.5 palmos of length, which makes a rake of around 1.3 to 1.5 rumos (2.05 to 2.30 m). Oliveira says that the midship frame should have a maximum breadth at the second deck of between 1/3 to 1/2 the keel length or, in other words, 6 to 9 rumos (9.24 to 13.86 m), and 8 rumos (12.32 m) as a fair value. He then goes on stating that the flat of the midship should be between 1/3 and 1/2 of the maximum breath, which is, for the 8 rumos established, 2.67 to 4 rumos (4.11 to 6.16 m).
|Floor||Number||Distance turn-of-the-bilge to keel||Theoretical Vales After Oliveira|
|C4||VIII||189 cm.||189 cm.|
|C5||VII||193 cm.||193 cm.|
|C6||VI||197 cm.||196 cm.|
|C7||V||200 cm.||199 cm.|