Some notes on different styles and principles for dating
Bridges are rather a forgotten area of architecture, particularly from a Scottish perspective, but detailed papers by Inglis are helpful. Gautier provided a comprehensive eighteenth century architectural guide. A modern assessment by Ruddock offers many insights into construction along with an inventory of the very oldest structures. Some architectural features help us to date all these old bridges, and there are thirty one bridges which are from the 16th century or earlier. These are listed separately. Little has been written on the shape of masonry arches themselves, yet this may be important.
1 Size of the span.
Inglis attributes considerable importance to the size of the span on multi-arch bridges: the arches became larger as time passed and the piers became smaller. He applies this to both England and Scotland and appears to describe a moderately reliable pattern: in general, bridges built prior to 1400 had arches under 30 feet wide, rising to 40 feet by 1450, and 50 feet by 1550. The older multi-arched bridges also had uniform span. These patterns are not very important for Scotland since very few bridges have survived from these earlier periods. However, the principle may contribute to maintenance history, since all bridges required extensive repairs every 70 to 100 years and the surviving span-width helps to determine whether the arch (or arches) were retained. This offers a measure of how much substance and style actually survived the serial repairs.
2. Shape of the arch ( also see Structure section)
The shape of the arch might be a better feature for dating than the span, and this is especially interesting with respect to pointed Gothic arches such as those at Haddington Abbey (left). Roman masonry arches were mostly semicircular, as were the earliest medieval arches. Architectural evolution away from this rounded Roman and Romanesque style to pointed Gothic happened in the 12th century, before many masonry bridges were built in Scotland. It follows that our earliest masonry arches were probably pointed rather than semicircular, and this 12th century Gothic shape would probably persist through to nearly the end of the 15th Century. Some time around then, the Scottish Renaissance arrived, perhaps best expressed by JamesIV at Linlithgow. There was a return to rounded arches in palaces and churches and it seems reasonable to propose that there was also a return to semi-circular and segmental arches on bridges. Certainly, in Scotland a pointed arch on a bridge is likely to be a 15th century or earlier design feature, whereas semicircular and segmental arches suggest 16th century or later. However, there is a need for caution; a pointed arch may represent a preservation of style through later reconstructions; it may be a copy or an outmoded feature on a 16th century new build, perhaps a function of remoteness from the European Renaissance. This rule about 15th century style can also be applied in England, where milder weather and better preservation means that a pointed arch sometimes suggests even greater age. We know from paintings that the 19 arches of London's medieval bridge were pointed. There are many British and European examples of Gothic arch remnants existing alongside younger semicircular or segmental replacements. Most of Scotland’s older masonry bridges are semi-circular but Gothic arches can be seen at Balgownie, Brechin,Tullibody, Dairsie, Haddington (Abbey Bridge), Cramond, Newbattle and Dumfries. Significantly, at Brechin, Dairsie and Dumfries only one pointed arch remains; in these cases the younger replacements are semi-circular or segmental. Gothic arches on bridges tend to be of a flatter, mezzo-arcuto shape rather than the sharper quinto-acuto which is common in abbeys and cathedrals.
Segmental (small slice of a circle) shape, as opposed to semicircular, also has modest significance. In the North of Scotland, a semicircular arch generally suggests a 16th to18th century date. (Bridge of Dye, left). After 1740 almost all new bridges were given a segmental arch. This evolution id best seen in the Hanoverian military bridges.
However, this rule does not apply in the South. Although north of Stirling it is rarer to see a segmental arch in a pre-1740 bridge (Inner Bridge in Fife is an important exception), in Southern Scotland there are many very old segmental arches such as Musselburgh (right) Haddington Nungate , Maidens, Hamilton, and Bothwell.
There are three caveats with respect to arch shape which are important: occasionally a segmental arch may be almost semi-circular and it may be sensible to classify it as the latter; sometimes a segmental arch may be stilted or raised and therefore resemble a semi-circular shape when it is clearly not; finally, a broken or 'hinged' semicircular arch sometimes resembles a pointed one, as can be seen with the bridge at Ayr. A further incidental problem is that photographs tend to distort the shape of an an arch, so care is needed. Notes on the structural aspects of these arch shapes can be found here.
Wheeled traffic started to arrive in the late 17th century. Ruddock notes that bridges built before about 1725 are seldom more than 13 ft wide. The exceptions were Berwick (17ft), Haddington Abbey (16ft), Bridge of Dee (14ft) and Dumfries (14ft). The Collection bridges, 1600-1680, were particularly narrow; it seems that 9ft wide was enough for attending church. After 1725 almost all bridges carrying roads into sizeable towns were built wider than 13ft. However, many earlier narrow bridges were subsequently widened. Sometimes this was part of a routine repair or rebuild. The original arch was ofen retained and the new arch ‘soldered-on’ Often the connecting line can be seen on the arch barrel. At Bishop's bridge in Perthshire (left) there are three arches.
4. Ribbed barrels
Ribbed soffits are a pre-reformation feature seen on twelve of the oldest bridges. Separated rings of the arch were constructed on centering and then slabs were overlaid (above: Tullibody). The feature is equally distributed, occurring on Gothic, segmental and semi-circular shapes. Ribbing was an economy: fewer arch rings, fewer keystones. Here, above, there are two orders of voussoir in the gothic arch. The upper one is often referred to as a countercourse and the inner or lower one is typically depressed. The apparent third order is, in fact, part of the ribbing. Most of Scotland’s ribbed bridges were built in the first half of the 16th century. There are twelve in all (see Lists) and there are three more at Inverness, Leith and Hawick which have had ribbed bridges in the past. However, there are a few later bridges which also have ribbing: Bothwell Bridge, Bridge of Dye (17th century) and Gannochy Bridge (late 18th century).
5. Ashlar and Rubble
Bridges before 1650 were mostly built in squared, coursed well dressed rubble masonry, or in ashlar usually with irregular stone size. ( left, Stirling) It is not easy to differentiate very weathered ancient ashlar from coursed, dressed well squared rubble, and serial repairs mean that often both exist side by side. Voussoirs and abutments are in the same materials. Chamfering of the voussoirs is a 16th century feature. There are usually simple cutwaters and large piers. Refuges are common, rising often from the cutwaters. String courses are a frequent feature and the parapets are almost always from a more recent date.
In the late 17th century a marked change took place: much courser rubble masonry was used, particularly for smaller bridges. This interlude lasted for 100 years. The random uncoursed rubble was very roughly dressed, if at all, although often the voussoirs were of whinstone and rather better finished than the spandrels and parapets. We can distinguish these bridges from those from 1800 onwards, when the quality of masonry improved again.
The voussoirs on the earlier rubble bridges had non-radial joints ie. they were not in line with the radius of the circle. Carrbridge (1717) on the left, is a good example. To the right is a limited quality sketch photo of the same bridge, in which an attempt has been made to demonstrate this. Each voussoir seems at a completely independent and unrelated angle relative to the central focus of the arch. This changed after about 1730, around the time when military bridges arrived, although one or two of Wade’s bridges are older-fashioned. Below left is Old Drip Bridge near Stirling, which is not in the catalogue because it was not built until 1765. The segmental arch is difficult to photograph head-on without getting wet feet, but it can be seen that the voussoirs are radially aligned to the focus of the circle.
6. 18th C. Military Bridges
The 18th century Highland military roads provide us with a separate group with interesting features. General Wade built 250 miles of road and 40 bridges, between 1725 and 1734, of which 17 remain and are present in this catalogue. There are recorded invoices for 35 bridges, of which 30 had a single arch. Major Caulfield built many more roads and bridges than Wade but he started in 1741 and only a little of his work was completed when the Roy survey was done. Two Caulfield roads were finished by the time of Roy’s survey and two more were being built during it. This is a small proportion of the 17 roads that are firmly attributed to the major. However, there are 11 Caulfield bridges, identifiable on Roy, and these are catalogued. Several more than that are catalogued because the bridge had a predecessor on the map. The military bridges were mainly of uncoursed random rubble, cheaper and faster to make, thus suiting a military need. They had plain vertical spandrels, seldom with a string course; they had radially aligned voussoirs; the arches were also of rubble, usually relatively larger in width compared to the rise and the span. The early 18th century Wade bridges of the Great Glen ( 1727) were routinely semicircular. Those of the Dunkeld to Inverness road, in the same year, were a mixture. Segmental arches are seen on the Crieff to Dalnacardoch Road(1730), at Amulree, Newton and Aberfeldy, and on the Corrieyairack pass. At Aberfeldy, the bridge is wholly atypical, reflecting Adam's design. Wade bridges had plumb spandrels in undressed uncoursed random rubble and most had horizontal decking. The workmanship was rather rough. They were between 11 and 14ft wide. Above left is the bridge at Etteridge near Newtonmore on the Stirling to Inverness Road (1730). A little further south, the bridge at Dalwhinnie may be the last to have non-radial voussoirs. Most of the Caulfield bridges, from 1741 onwards, were segmental and exactly 12ft wide; they were humped and had gently sloping parapets up to the crown; they were better constructed in dressed, sometimes squared, random rubble and were also more elegant, with gentle lines and splayed approaches. Below is Fraser's Bridge on the 1749 Caulfield military road from Blairgowrie to Braemar: a two span rubble segmental arch with wide radially aligned voussoirs. Many of Caulfield’s bridges had an interesting texture of uncoursed large boulders with small ones (Gallets) in between.
by Neil Philips. uk-wildlife.co.uk
These bridges were impressive works of civil engineering that have stood the test of time. Yet, Taylor, in his definitive ‘Military Roads of Scotland’ encapsulates something more: “Although considerations of natural beauty were far from the minds of the military road makers …...The bridges over Tay, Tummel, Garry, Spey at Garbhamor, Spean and Findhorn at Dulsie, have a romantic grace and beauty which almost belie their usefulness and efficiency"
To be differentiated from -
The military bridges as a distinct group have to be differentiated from the parliamentary bridges which arrived after 1803 and are not in this catalogue. The Commission for Highland Roads and Bridges was established by an act of Parliament, and Thomas Telford was the chief engineer. He set out very firm specifications for different types of parliamentary bridge. Types 1 to 3 were rubble built and of the same size range. The voussoirs were of quality dressed stone, often ashlar. Type 1 was humped but flatter levelled approaches were generally typical of types 2 and 3. All had slightly outward sloping( battered) spandrels or abutments. On type 3 bridges each abutment was stepped into a greater outward slope, while the spandrels were plumb; the vertical step ran from parapet to springing. This was the so called 'plumb and batter' build. The type 4 parliamentary bridge cannot be confused with the older military bridges, because it is very much larger, ashlar built and multi-arched, with cutwaters merging into the refuges. Large segmental arches were in beautifully dressed stone with recessed voussoirs. The spandrels, approaches and abutments were were in coursed, dressed squared rubble. Good examples are at at Dunkeld, Potarch, Dunans and Invermoriston. In 1829 Telford noted that 1117 bridges had been built by the Commission.
Commission of Supply bridges (18th and also early 19th century) have a similar style. Much of the bridgework in the South was repair and maintenance . However, there were quite a few new-builds. Good examples can be seen at Barskimming, Coyle, Barr and Ricarton: large wide segmental arches with ashlar, recessed voussoirs and coursed rubble spandrels and approaches. At Ricarton, south of Kilmarnock, the spandrels are in ashlar. These bridges had much in common with the Telford styles and at Barr (left) a plumb and batter can be seen to the right hand side. In general, the quality of stone used for voussoirs and abutments improved from 1750 onwards, with recessed ashlar arches becoming steadily more common.
In general, 19th century builds had an improved quality of stonework. At first, ashlar became common for the voussoirs, but later it became routine for the entire structure. The masonry became more decorative and well finished, often with balustraded parapets. Low segmental or eliptical arches arrived, and these were usually stilted on well finished piers.
6. Heraldry and date inscriptions.
Heraldry and inscription are important – but a great deal caution is required; frequently the heraldic carving was retained through thick and thin -even being transferred to entirely new builds, or moved from one side of the bridge to the other when rebuilding or widening was taking place. It may be that the single most important aspect of dating a bridge is that datestones should be viewed with suspicion. More often than not they refer to a repair date. Throughout history, it seems it was quite routine to include a date plaque at the time of any major repair or restructuring. This can be very misleading.
Examples of dating enigmas and inconsistencies.
We know that in 1250, the first bridge at Stirling was adjacent to the present medieval bridge. It may have been there for some time before that date. It is confirmed on Mathew Paris's map. The bridge was destroyed in 1297 in the Battle of Stirling Bridge. Ferryboats were in place for the next 100 years. Documents tell us that the present Old Stirling Bridge was built in the early 15th century (Ad fabricam payments in 1409 and 1415). That this new bridge might be "broken" in 1424, suggests it was still made of wood at that time. Today, the central arch of 56 ft and the variable span (56:48:38) suggests a late 16th century date. We also know that major ‘re-formation' was carried out in 1542 and that the bridge was again ruinous in 1598. One might speculate that the same masonry might be re-used in any reconstruction, with some parts retained. So, this typifies the interesting question of dating: do we call this a 13th century bridge, or a 15th century bridge, or a 16th century bridge?
Even in the case of single arch bridges there is room to be suspicious of too large an arch. Balgownie Bridge on the River Don has claims to the early 14th century, but it has a span of 70 feet which makes this date most unlikely. There was a series of major repairs in 1444 which would be compatible with the gothic arch. Poor maintenance at the time of the Reformation led to an almost complete reconstruction by the local Town Council in 1605.
In contrast, a Dumfries Bridge was under construction in 1432 (the earlier Dervorgilla Bridge had been swept away.) We are told that in the floods of 1621, this 15th century bridge was also swept away. Yet today there remains a single gothic arch, which is significant, and although the other, younger arches are semicircular, they are uniformly about 30 feet wide with very heavy piers. Today, Dumfries resembles a 15th century bridge rather than one from the 17th century. Perhaps the regular small span was retained and a single arch at one end, survived the floods.
The bridge at Tullibody over the Devon Water near Stirling is thought to date from 1520. Robert Spittal, royal tailor to Margaret Tudor and James IV, is reputed to have built Doune and Bannockburn bridges as well as Tullibody. One has to wonder why he chose such very different architecture for all three creations: Doune (right) has large semicircular arches, yet Tullibody has two small 18 foot gothic arches with a very substantial pier between. Bannockburn is very different from both. The pointed arches at Tullibody are also important and it is also strange that a single large arch was not chosen to span the river, as certainly would have been possible in 1520. Perhaps we can speculate that the gothic remnants at Tullibody, with the tiny spans, survive from an even earlier period? Much of what was attributed to Robert Spittal is nebulous and of indeterminate date.
Dairsie Bridge in Fife carries the heraldry of the Bishop of St.Andrews, James Beaton. This would date the bridge to 1530. It has one Gothic arch and two uneven semi-circular ones. The Gothic arch might suggest an earlier date. In fact, a Lord High Treasurer document confirms that a bridge was there, at least in 1496, in that a sum of money was given to ' ane pur wif at the brig of Dersie as the king raid by'. As is often the case, the heraldry may refer to a major restructuring rather than a new build.
Finally, Haddington Abbey Bridge over the Tweed is wonderfully preserved and has three ribbed gothic arches. There is a modest 37ft span. There is a date carving of 1870 which no doubt refers to a major overhaul with more modern facing on the spandrels. Archaeology has revealed three important surface reconstructions over a very long history. It is reputed to be 16th century although Ingles attributed an earlier date. Fifteenth century is more probable. Despite so many rebuilds the original design has been retained. There is one strange aspect to this: the bridge is 16ft wide, parapet to parapet, and although some widening can be seen, the original width appears to have been about 15 ft. This is very wide for a 15th century structure which is not part of a major route.