Slag-glazed stones were found where William Conner stands along the wall of Spruce Hill during an investigation of the ancient hilltop "fort" with David Orr. This site is at "Point F" on the Squier and Davis Map (see below) , where they reported finding evidence of intense fires. (Photo by David Orr)
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Spruce Hill Investigation April, 1992 David Orr examines glazed stones in the wall of Spruce Hill. This is a closer view of the same site as above. Glazed stones found here could have only been produced in a charcoal furnace where reducing conditions and temperatures at 1260 degrees C (2300 F) would permit iron oxide Celedon glazes to form. (Photo by author) |
Spruce Hill as mapped by Squier and Davis in 1847. The narrow neck of the plateau at bottom, "the isthmus," was where many furnaces were located and where Cahoon casting mold was found. At "F" on the map, Squier and Davis reported seeing "strong traces of fire" in "two or three small mounds of stone, which were burned throughout." They also said many stone mounds along the wall exhibited marks of intense heat, vitrifying the surfaces of the stones and that "light, porous scoriae are abundant in the centers of some of these piles."
Two Pit Furnace Types Found in South Central Ohio
Archaeological riches were found heavily deposited in south central (SCO) and southwestern Ohio (SWO) by American settlers of European descent who arrived in the 1790s, after the Indians departed. Mounds were found to contain exotic grave goods of meteoric iron, copper and stone. Fields there still yield flint tools and projectile points.
The archetypical mounds of the far-flung Adena and Hopewell cultures are both located in Ross County (SCO). As the great original SCO forest was cut back, groups of mounds enclosed by earthwork walls and wide, lengthy graded avenues were revealed. Large areas of some hilltops and plateaus were found enclosed by walls of earth or piled stone. High-temperature furnaces were found both inside mounds and inside piled stone walls of enclosures..
All of this gave rise to speculation that not the Indians, but perhaps ancient visitors from the Old World, came before Columbus and created all of these works. Some said the mounds and earthworks proved the Lost Tribes of Israel must have reached America and became the Mound Builders. When pit furnaces were found in Ross County in 1811, and it was apparent high temperatures were attained in them, it added even more to the belief in the ancient visitors.
Since most prehistoric fire pits have been completely destroyed, vandalized or completely excavated by investigators who could make little sense of their pyrogenic remains, studying them is difficult. However, when considering what evidence is available, it seems clear that these furnaces fall into two types:
furnaces or kilns found in mounds of two SWO earthwork groups in Hamilton County; the Turner Mound Group near Milford and the Edwards Farm Group near Reading.
furnace pits found in the piled stone walls of Spruce Hill, an ancient "hill fort" in Ross County, where evidence indicates the melting and casting of native copper.
The two groups above are furnaces unknown to history are therefore are prehistoric. They represent a wealth of archaeo-metallurgical remains almost unknown to America's community of professional archaeologists. It seems quite amazing to this writer that such a variety of enigmatic high temperature pit furnaces should exist in a relatively small region of central and southern Ohio. It is no wonder earlier investigators were confused by this situation.
A large industrial site was found in 1811 on top of Spruce Hill, a walled hilltop in Ross County, some 12 southwest of Chillicothe, the county seat. This discovery was brought to the attention of James Foster, editor of the Scioto Gazette, a Chillicothe newspaper.
After visiting the site, Foster wrote a in letter (found stuck inside a scientific journal published in 1814) that he wasn't sure what the furnaces had been used to produce, but said ashes in the furnaces as resembled those of a blacksmith's forge. Foster said 30 furnaces were found in the stone-pile walls which encloses 140 acres of the hilltop plateau. Because of the remains of huge trees which had been growing along the walls, Foster concluded that the furnaces must be ancient.
Indeed, quite recent archaeological work at Spruce Hill found that evidence still exists to establish that temperatures around 2300 degrees F may have been achieved in antiquity. Rocks coated with green and gray-green iron slag occur in the same archaeological setting as artifacts of the Hopewell people, according to Bret Ruby, the US National Park Service archaeologist who made several excavations at Spruce Hill in 1995 and 1996.
And not only were such temperatures reached, but they had to have been reached inside an pit sufficiently enclosed to permit a reducing atmosphere to exist, rich in carbon monoxide and carbon dioxide. To achieve a high concentration of these hot gases, charcoal fuel would be necessary.
Also, a material rich in silicon and iron oxides, such as bog iron ore, would have had to have been processed in a reducing atmosphere in these furnaces for the greenish slag to result. Well-baked lumps of heavy red clay (probably the bog ore) are found in association with the green-glazed stones at Spruce Hill. The Cahoon Mold, found there in 1993, is a prime example of what seems to be bog ore.
Arlington Mallery offered proof in Lost America that metallic copper from the Great Lakes region, known to have been used by the Hopewell people, was melted and cast to form some of their larger copper artifacts. The author of this web site now believes a "smoking gun" to back up Mallery's evidence has been found at Spruce Hill in Ross County, Ohio.
It now seems evident (as of May, 2000) to this writer that with the discovery of the Cahoon mold, good evidence exists that native copper from Great Lakes sources was melted and cast at Spruce Hill. For a discussion of copper casting as reported by Mallery and others, and also to view a photo of the Cahoon Mold, go to Copper Casting In Ancient America? in this web site.
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Glacial Loess Underlies Plateau Park Service archaeologist Ruby, on left, shows a rain-soaked APG Society tour group his 1996 excavation along the "isthmus" of the Spruce Hill plateau. Ruby said the excavation proves the Hopewell workers carried stones from the hillside out over the plateau to create the isthmus portion of the stone wall. This tour took place November 22, 1996.There is no stone outcrop on the isthmus because the level field here is composed of a thin layer of soil over several feet of glacial loess. The plateau was created by the leveling action of the Illinois Glacier. Thousands of years later, the Wisconsin Glacier contributed the wind-blown loess. |
In 1896, 31 fire pits were discovered in the floor of a mound (Mound 3) being excavated at the Turner Mound group near Milford in Hamilton County, Ohio. Many of these pits were a part of a pit-and-tunnel system which joined many of the pits with one other pit (p-p), while many others weren't paired (p). Variations in both the two-pit sets (p-p) and the single pits (p), suggested that both configurations may have been used for more than one purpose.
Since the discovery of Turner Mound 3 and its furnaces, investigators have speculated about their use, mostly in vain. But a corroded lump of copper was also found there also, suggesting that perhaps lumps of copper from the ancient Great Lakes mines could have been melted for casting into desired shapes. Certainly, an analysis of the Turner copper lump showed that it had been heated to over 1,000 degrees Celsius (copper melts at 1083 degrees C). But no "smoking gun" was found to prove conclusively that copper was melted and cast, such as crucibles, molds or tongs was found at Mound 3.
Experimental furnaces, copying the designs of the Mound 3 pits, have been operated by investigators and temperatures as high as 600 degree Fahrenheit were reached with natural draft. One investigator using a forced air draft in a replica of a single pit furnace (p) was able to reach an astonishing 1535 degrees Celsius (the melting point of steel).
However, in the opinion of the author of this web site, the Turner pits were too large and deep to suggest the melting of native copper for casting. Peruvian prehistoric furnaces used to melt smelted copper for casting were quite shallow by comparison, allowing the workers to use green wood tongs to remove the hot crucibles from the fire to the casting mold. The Turner pits, ranging from 3 to 9 feet deep and 1.5 to 4 feet wide, seem quite impractical for lifting out crucibles of molten copper. A typical Peruvian copper processing furnace was only 10 inches deep.
Copper Casting In Ancient America?
