COMMUNITY archaeologists have discovered two sites of national significance – unlike any other in railway archaeology – which could “rewrite the understanding” of early wooden railways and salt pans.

During the first week of September, archaeologists and community members from the 1722 Waggonway Project returned to two sites where exploratory digs had been carried out, searching for remnants of the salt and coal industries which were the backbone of the country in the 17th and 18th centuries.

The latest phase of archaeology at both sites has been described by experts as “rare”, “unique” and of “national importance”.

The primary site of Scotland’s earliest railway, the Tranent Waggonway, where the Waggonway path crosses the Prestonpans battlefield between Cockenzie and Meadowmill, was constructed in 1722 by William Dickinson.

Its function was to bring coal from the pits at Tranent to the salt pans at Cockenzie and Port Seton.

During the dig, in which archaeologists were aiming to find the original track-bed structure, the main trench revealed three wooden railways, each one lying immediately on top of the last in an apparent multiple early upgrade over a short period of time.

Consisting of crudely cut timbers, these upgrades included a change of gauge, from an initial 3ft 3in in the first phase to 4ft 0in in the second and third phases – modern railways are 4ft 8.5in.

The discovery has been described as unlike any other in railway archaeology.

Some sleeper and rail timber, including the remains of a timber ‘raft’ foundation structure used on ground which was wet at the time, was found to be preserved in its original location, with the shape of these clearly visible in the ground, one metre beneath the present-day ground surface.

Research conducted by the Waggonway Project has allowed the group to begin establishing each phase of railway building to a particular date with clusters of activity in the soon-to-be-published William Dickinson Journals (1720-1745), now appearing to relate to three distinct phases of railway construction.

This data is being mapped for these clusters, which shows an initial build in 1722-24, a second in 1728-30, and a third in 1743-44.

A full archaeological report will be published once all post-excavation work and research is complete.

Anthony Leslie Dawson, early railway historian, said: “It’s not every day that you see railway history being rewritten before your eyes.

“The site is of national significance: a three-phase wooden waggonway, stacked on top of the other, is without precedent.

“Whilst we know these railways had a limited lifespan due to their method of construction, to see this process of continual replacement and upgrade – including a change of gauge – in the archaeological record is outstanding.

“The excavation has shown that these waggonways are far more complex than the single-phase structures previously excavated, and the survival of timber on site including joints, helps us further understand the construction of these early railways.

“It is rare that on a single site, the history of a railway – reflecting in a microcosm national trends in railway technology – can be traced, from various phases of timber railway to an iron railway, itself of more than one phase.

“The 1722 Waggonway Project has, over only three days, added immensely to our knowledge about early wooden railways. It has rewritten our understanding of Scottish railway history.”

The salt pan dig on the Cockenzie shoreline also surpassed all expectations, with two phases of salt making being revealed, spanning from 1630 to the last phase of use around 1780, which is unique in Scotland.

The phases were well preserved and the deep ash pits and remnants of the iron grate, upon which coal burned in the furnaces, survived in “amazing” condition.

Doors in the sides and seaward end of the building were also discovered, believed to have been used for bringing in materials for the operation and repair of the salt pan itself.

Evidence was found that the building had been repurposed as a tenement during the 19th century, which survived until the 1930s when it was largely demolished.

Joanna Hambly, of SCAPE Trust and the University of St Andrews, said: “This is an incredibly rare survival of what was once a common sight around the Forth Estuary region. The only other example of this date comes from Bo’ness and is buried beneath a later building.

“It’s incredibly exciting to think that in future it may be possible to unpick these technological innovations in the archaeological record, rather than relying on documentary sources, which has been the case until now.

“The building is ideally located on the coastal path and John Muir Way and so there is enormous potential to conserve and interpret it to tell the story of Cockenzie’s industrial past.”

Alan Braby, archaeologist and illustrator, said: “The route of the 1722 Waggonway exceeded all our wildest expectations.

“We knew we had the waggonway in previous trial trenches, but to discover it had three phases of rebuilding was certainly unexpected.

“The preservation of the remains was amazing, and already post-excavation work is hinting at even more unexpected revelations.”

Ed Bethune, historian and Waggonway group chairman, said: “The archaeology here is second to none, and without doubt they are incredibly significant industrial sites which can shine a spotlight on the early-modern history of Scottish industry, not to mention the wider field of railway and salt-making history.

“We are excited to see what further information these and other locations can yield in future digs.”

Stephanie Leith, heritage officer at East Lothian Council, said: “The discovery of three sets of wooden railways from the early 18th century is a find of huge importance to our understanding of Scotland’s earliest railway and how it developed.”