The Heat of Battle

Who Turned Ancient Hill Forts to Glass?

In 1991, I was traveling through Scotland to see for myself some of that ancient nation’s most intriguing mysteries. Foremost among them was Craig Phadrig, an early Dark Ages site crowning a forested hill rising 564 feet above the western edge of Inverness, Britain’s northernmost city. It overlooks the Beauly Firth inlet to the north and the mouth of the River Ness to the northeast. The view—as panoramic as it was commanding—suggested the old structure’s original military intentions. The ruin itself seemed unexceptional in every respect. Its inner walls of crudely piled rocks enclosed an oval area 246 by 75 feet, rising an unimpressive 3 feet, 11 inches high. Beyond it lay another, outer rampart with sections of a third to the east.

A King Bridei mac Maelchon was supposed to have ruled over the Keltic Picts from this place for 34 years during the late sixth century; and Pictish metal-working tools, plus French pottery of 200 years later, have been found there, but nothing more. These common details are incidental to the prosaic hill fort’s true significance, which appears only on closer examination of its clumsy, unmortated stonework: huge blocks had been fused with smaller rubble to form a hard, glassy mass. The rock face had been literally melted into what is called ‘vitrification,’ which is defined as: “A molecular change in the surface of a rock caused by high temperatures, which transform the naturally rough surface to form a bright and shiny finish… This molecular modification caused by [high] temperatures produces a skin or surface layer on the rock… The combined use of molding and heat have given the rough stone a mirror-like finish [and] its metallic sheen.” ( 61s, “Vitrified Rocks and Stones in the Inca Vestiges”).

I specifically chose to visit Craig Phadrig, because—of all the other, seventy or so such locations in Scotland—it was among the best preserved, a relatively pristine representative of the Highlands’ so-called “vitrified forts.” How their prehistoric builders achieved, applied, and sufficiently sustained temperatures well above 1,000 degrees Fahrenheit required for vitrification was at odds with known Keltic furnaces, which reached no higher than a quarter of that intensity. Last May, however, “archaeologists believe that they have solved the mystery of an Iron Age fort in which stones had melted in a process termed vitrification.

“The team of experts studied the vitrified fort, known as Dun Deardail, in the Highlands, near Ben Nevis [at 4,411 feet, Scotland’s highest mountain], and have concluded that they can explain how its stones became molten and melted. The experts from the Forest Enterprise Scotland, working with Stirling University, believe that they have solved the enigma. They believe that a large-scale wooden structure over the stone walls was set alight, and the blaze reached such a temperature that it burned the stones. Now the team led by an archaeologist from the University of Stirling has offered what they believe is the most plausible explanation for the phenomenon of the vitrification of stone citadels.

“The study has shown that a timber superstructure, which included ramparts and towers, was set alight, and the resulting blaze heated the stones. The fire was so intense that is was able to melt stones because of the anaerobic environment that developed, as the flames burned down into the stones. The absence of oxygen in the anaerobic conditions made the fire much more intense and allowed it to reach the temperatures that would have burned the slabs until they melted and fused” (

“We’ve learned that the technology required to create the vitrified forts was not extraordinary,” concludes science writer Brian Dunning, Executive Director of Skeptoid Media. “Nothing found at the sites requires any reexamination of the history of knowledge” (

Sadly, the University of Stirling experiment failed to vitrify anything more than a tiny handful of rubble, far short of the vitrification covering even the smallest of Scotland’s six dozen forts; the archaeologists were simply unable to keep their fires burning long enough to sustain the necessary temperatures. Their attempt was, moreover, redundant, and served only to underscore a similar experiment undertaken 84 years earlier by Vere Gordon Childe, an archaeologist at the University of Edinburgh.

In March 1934, they “set about trying to replicate the process that led to the vitrified stones of Scotland,” writes author Nick Redfern. “They carefully constructed a series of walls that were comprised of fire-clay bricks, timber, and basalt rubble. They then proceeded to place no less than four tons of brushwood, and extra timber, against the walls and set them on fire.”

“The experimental wall was six feet wide and high,” according to the 1966-67 edition of The Proceedings of the Society of Antiquaries of Scotland, “with horizontal timbers interlaced with stone slabs. After ignition through brushwood fires around the wall face, the wall began to burn and after three hours it collapsed. The core of basalt rubble became red-hot, probably reaching 800 to 1200°C, and after excavation the bottom part of the rubble was found to be vitrified, with rock droplets and casts of timber preserved” (Nick Redfern, “Ancient War Fires,” Atlantis Rising #118, July-August 2016).

A few, melted droplets were the sole results of more than four tons of burning brushwood and extra timber. Clearly, a concentrated, far more powerful, longer-lasting heat source had vitrified Craig Phadrig and its associated fortresses. Building on the Childe and Thorneycroft effort, Dr. Ian Ralston (at Edinburgh University’s Department of Archaeology) undertook an even more ambitious project in northeast Scotland, during 1980, when he built his own 25-foot-long, partial recreation of a stone fort.

“Professional dry-stone-wallers toiled for days to build the wall of rock laced with timber,” which was set alight. “After several hours and many tons of wood, a load of old furniture has to be commandeered from the local dustman, as the only way to keep the temperature up. Later, another consignment of wood, the sixth of the day, arrives to keep the fires burning. As night falls over Aberdeen, weary helpers begin to realize the true extent of the mystery of the vitrified forts, to wonder not only how the fort builders could achieve the searing temperatures needed to melt the rock, but how they managed to drag vast quantities of wood up to the tops of the hills with only primitive transport. The morning after… 22 hours after the first fire was lit… at first sight, the result looks disappointing. There are no ramparts of fused stone. The search is now on for any rocks that have melted” ( PIoYZLZySzI, Arthur C. Clarke’s Mysterious World).

The handful of specimens Dr. Ralston retrieved from the blaze fit into the lid of a small, cardboard carton, with room to spare. He did prove, however, that piling on flaming timbers could melt stone. He likewise demonstrated that burning at least half of Scotland’s original, 30,000 square miles of pine forests would have been necessary to vitrify its 70 or more hill forts, as established by the ratio of his Aberdeen fire to the very few, vitrified pebbles and drops he recovered. His experiment also revealed that the coolest part of such fires occurs at their bottom or base, where heat efficiency is lowest and chances of resulting vitrification are minimal.

Official radiocarbon dates obtained by his academic colleagues at various vitrified sites range from the sixth century BCE to fourth century CE. This unmanageably broad and vague time span enfolds numerous cultures that rose and fell across northern Britain, making any connections with any one, or even a combination of some of them, to the vitrified forts impossible to ascertain. Dr. Ralston himself confesses that, “the process has no chronological significance and is found during both Iron Age and Early Medieval Forts in Scotland” (Ralston, Ian. Celtic Fortifications. UK: Tempus, 2006). Moreover, C-14 testing cannot date any of the vitrified locations, save by presumed reference from organic materials found on site. As such, half-devoured chicken bones radiocarbon dated at Craig Phadrig to 300 BCE mean only that someone enjoyed an Iron Age meal there; concluding from them that the structure was actually built at that time is jumping to conclusions, minus any basis in applicable data. Due to the sealant nature of their vitrification, the forts themselves are “virtually impenetrable to erosion, meaning that the true age of these miraculous structures may be far, far older than we are led to believe” ( S75GzpTbO0A&t=52s, Ancient Stone Forts “Turned To Glass” Found In Scotland?).

They are, after all, cultural anomalies, possessing nothing in common with, and much less distinctive of, the Keltic, Pictish or Early Medieval Scotts cultures assigned to them by archaeologists without credible cause. More likely, these uncharacteristic places belonged to an older period. The forts were more likely built by a Bronze Age society.

This period, indeed, witnessed widespread burning across Europe and the Near East, as documented in the author’s Survivors of Atlantis (VT: Bear & Company, 2004). Among the findings at the Cambridgeshire site were intricately decorated tiles made from lime tree bark, indicative of a high culture. As recently as 2016, Scottish archaeologists discovered one of the largest Bronze Age wheels to have ever been unearthed anywhere near the same excavation. The wheel measures a meter (3.28 feet) in diameter and 3.5 centimeters (1.38 inches) thick.

Although mainstream scholars presume the vitrified forts are exclusively Keltic, especially Pictish, the same structures are found outside Scotland, in County Londonderry and County Cavan, Ireland. They occur in other parts of the world, sometimes far removed from the British Isles. There are more than 200 on the European Continent alone, in France, at Sainte-Suzanne (Mayenne), Châteauvieux (near Pionnat), Péran, La Courbe, Sainte-Suzanne, Puy de Gaudy, and at Thauron.

Contradicting conventional identification of vitrified forts entirely with Europe’s Iron Age and Early Medieval Period—unmistakable evidence of a military installation’s rock face having been deliberately melted during prehistory was excavated at Ohio, in 1890, by our country’s foremost archaeologists of the time, E.G. Squier and Edwin Davis. The stone fort they investigated—dismantled in the following century—was near Bourneville. “It occupies the summit of a lofty, detached hill twelve miles west of Chillicothe,” according to a contemporaneous article in American Antiquarian (Peet, Stephen D. 13:189–224, 1891).

“The hill is not far from 40 feet in height. It is remarkable for the abruptness of its sides. It projects midway into the broad valley of Paint Creek and is a conspicuous object from every point of view. The defenses consist of a wall of stone, which is carried around the hill a little below the brow, cutting off the spurs but extending across the neck that connects the hill with the range beyond. The wall is a rude one, giving little evidence that the stones were placed upon one another, so as to present vertical faces…” This description of the Bourneville site is a mirror image of Craig Phadrig or most European hill forts.

American Antiquarian goes on to report Squier’s and Davis’s observation that the Ohio structure exhibited “the marks of intense heat, which has vitrified the surfaces of the stones and fused them together. Strong traces of fire are visible at other places on the wall, the point commanding the broadest extent of country. Here are two or three small stone mounds that seem burned throughout. Nothing is more certain that that powerful fires have been maintained for considerable periods at numerous points on the hill.”

Pre-Columbian vitrification also took place in South America, at the Incas’ most important sacred centers. Visitors to their Peruvian capital at Cuzco may still see the great, pre-Conquest walls of Loreto Street, their vitrified blocks fitted together with a jeweler’s precision. Near the city is Amaru Machay, “Cave of Serpents.” a subterranean temple of worked andesite, an extremely hard and difficult stone for carving, but nonetheless melted under controlled high heat conditions.

While the Incas occupied these impressive locations, they did not build them. Even orthodox scholars admit that Sacsayhuamán was raised by construction engineers of the little known Killke Culture that flourished in the Cuzco area, centuries before the Inca conquered it. When tour guide Brien Foerster visited Amaru Machay, he observed how “the sculpted surfaces… with the heavy weathering patterns, show clearly that this place is much older than the presence of the Inca, [who] arrived here in AD 1200. But any real thinker will note that the weathering patterns of the stone itself predates them by a very long period of time” (, “Amaru Machay: Temple Of The Serpents In Cusco”).

A sixteenth-century scholar, William O’Flaherty, recorded that the Milesians, pre-Celtic invaders of Ireland, arrived long before 1000 BCE. Their leader was Eremon, an apparent linguistic inflection of the Classical Greek Euaemon, the fourth king of Atlantis cited by Plato in his dialogue, the Kritias. The Milesians were said to have originated in Annwn, famed throughout Keltic myth as the “Land under Wave,” from the Brythonic an, meaning “abyss” or “depths,” and dwfn, meaning “world” or “realm.” Also known as the “Revolving Castle” (Caer Sidi), it was a fortified island of great natural beauty, with freshwater streams and a circular-shaped city surrounded by concentric walls lavishly decorated with gleaming sheets of precious metal. This description matches point for point a similarly detailed account of Atlantis in Plato’s same dialogue.

Caer Sidi’s central palace was called Emahin Ablach, “Emhain of the Apple Trees”. Eremon’s home-away-from-home, however, was at the Isle of Man, where Reel Castle allegedly covers his grave site, and one of Ireland’s very few surviving vitrified forts may still be found. In the lost Druidic “Books of Pheryllt,” and “Writings of Pridian,” Emahin Ablach, Ynys Avallach, or Avallenau were “more ancient than the Flood, when all the rest of mankind had been overwhelmed.” Cogently, Avallenau (the British Avalon) was additionally referred to as Ynys-vitrius, the “Island of Glass Towers,” an isle of the dead, formerly the site of a great kingdom in the Atlantic Ocean. Ireland’s vitrified forts are referenced by Ynys-vitrius, the sunken “Island of Glass Towers.”

Additional oral tradition reaffirms an Atlantean interpretation in pre-Christian Ireland’s most popular deity. Lugh arrived from Murias, an island kingdom of high magic that nonetheless sank to the bottom of the Atlantic Ocean for the iniquity of its over-reaching sorcerers. Referred to as Ildánach (“skilled in many arts”), Lugh was a sun god, who wielded Sleg, an all-powerful spear that spat great swaths of fire.

These mythic references suggest the arrival of Middle Bronze Age Atlanteans operating high-intensity lenses or mirrors that concentrated rays of sunlight on rock exteriors to melt them. To what end, however, we cannot guess.

By Frank Joseph