Clamshell and labor crew excavating west of the wheelpit .
The dam was at the line of boulders between the the
left side of the machine and high mound of earth.
Robbins started his excavations at the heating hearths. There in the fill and rubble he found refractory bricks that had been used to line the inside of the furnace and oven. He also found chimney brick, mortar, metal waste and cinders. The base was an unusual shape made of large flat surfaced stones. Some of the original bricks were still mortared into them. In the first hour of digging he found the first artifact 'a good sized nail ' and won a bet with Amelia Peabody.
Because the breached dam had washed out tons of gravel and boulders, the mill foundations and wheel pit were buried under a deep overburden. Robbins had his laborers excavate with pick and shovel to evaluate the depths of rubble and fill and find the original stonewalls and foundations. After they determined the alignments the overburden soils and debris were excavated by a mechanical crane with a clamshell bucket. Robbins felt that without this machine it would have been impossible to successfully excavate the ruins.
The exploratory hand excavation followed the stone foundation walls of a long wheel pit. On its easterly side they found a stone walled pit where the waterwheel shaft had its bearing. Two large stones, each with a set of heavy bolts, made up a base to support and anchor the end of the shaft.
Clamshell and labor crew excavating west of the wheelpit
.
The dam was at the line of boulders between the the
left side of the machine and high mound of earth.
At the westerly side of the main wheelpit Robbins was surprised that there was no similar base and support for the other end of the shaft. Instead, he found a recess in the western wall of the wheelpit and a stone foundation wall that outlined the rolling and cutting area within the mill building.
South of this walled area and extending to the dam base stones he found many specimens of barrel hoops and uncovered an entire bundle of twenty-four hoops of assorted sizes wrapped with strips of metal. He also found trimmings of metal cut from rolling and slitting operations. These artifacts were all buried under eight to ten feet of soil and boulders from the washed out dam.
But the most interesting and surprising discovery proved to be the great stone wheelpit where the waterwheel turned. It had been filled nearly to the top with rubble and soils washed into it from the dam so there was no way to know how big it was. As excavation proceeded Robbins and his men were amazed to find it was forty feet long, seven feet wide and twenty feet deep. He later noted in his report to Amelia Peabody: 'this stone waterwheel pit is probably one of the largest ever built in this country.' But as Robbins and his crew dug deeper into the pit they were further amazed to discover a large section of the waterwheel buried at the bottom and submerged under water.
A section of the old waterwheel was found submerged under
water at the bottom of the wheelpit. The broken ends of the
sides of the wheel are visible as narrow pieces at the back,tied
together by a long iron rod. The four broken members rising
in the water are what was left of the big wheel spokes.
They managed to pump out enough water so Robbins could measure it, sketch the details of its construction and determine the materials used to build it. He calculated that the whole wheel had been thirty-six feet in diameter and five feet wide with twelve sets of spokes. It was made of oak except for the pine boards that sheathed the wheel to form the bottom of the buckets. Segments of the outer shroud members were connected with iron plates and bolts and were held together by long tie bolts with nuts and washers. It may well have been the largest wheel of its kind that ever operated in New England.
Roland Robbins drew this sketch of the section of waterwheel
in 1954.
It shows materials, dimensions and details of construction of the wheel.
In his report to Miss Peabody Robbins said: 'the thirty-six foot overshot waterwheel .. can be classed as quite unique because of its trememdous size..[and] .such a relic is worthy of a museum where it can be studied and pondered by historians or students.'
But, as things turned out it could not be removed. Most of the easterly wheelpit wall had a 36 inch bulge in it so the whole wall might collapse at any moment. This created a dangerous condition for workmen if they tried any further excavation in the pit. Besides that, the bottom of the pit had about two feet of water that could not be drawn down even with three pumps working. So, in the end, the section of the ancient Dover Union Iron Company waterwheel was left where discovered, It was not removed and to this day is interred in the pit where it once turned.
Reconstructing the great stone dam proved to be one of the major efforts in RobbinÕs restoration work. Most of it had collapsed and washed out over the years and when Robbins arrived there was little left of its original structure.
He described the ruined dam and some of the difficulties in a report to Amelia Peabody:
'The entire front of the dam had toppled from its original height. While the northwesterly corner could claim some of its original stonework, it lacked more than a dozen feet of its upper structure. As the front wall extended easterly of the northwesterly corner, it did not fare as well. Its stones had toppled nearly to the working surface of the main building, a distance of about twenty-three feet.
The intact base being buried below the rubble which tumbled from the upper wall, was exczvated by the mechanical clamshell. These excavations created heaps of boulders and soils. Adding these piles of rubble stone and gravel soils to the mounds of similar fill, which we had exhumed during the earlier excavations at the waterwheel pit and the main building sites, and we had a perplexing problem. How could a sixteen ton, cumbersome, mechanical crane play leap-frog over miniature mountains of displaced earth?'
Amid all the rubble Robbins found a twelve foot high section of original dam stonework that had survived. It was below the spillway opening directly in back of the wheelpit and extended easterly to the rip rap buttress where the dam bends. Miss Peabody asked him to save it as an example of the original work, so Robbins worked around it as he reconstructed the dam.
He found other original stonework on the westerly wall and left this undisturbed too despite the fact that it had a prominent bulge*. Amelia said it would 'lend authentic realism to the restoration'.
In excavating along the front face of the dam Robbins found that its base extended more than six feet below finish grade and was about eight feet thick at the bottom. The whole dam had been constructed with stones and boulders set dry with no cement, so Robbins reconstructed the dam to have the same appearance. The stonemason used stones and boulders from the site and set them dry. But back side of the new stonework was reinforced by covering it with concrete where it would be unseen.
View from the top of the dam when work was substantially
complete. The dangerous bulge in the wheelpit wall is clearly
visible. The main gearwheel turned in the smaller wheelpit to
the left. It was on the same shaft as the 36 foot overshot
waterwheel. The shallow walled area to the left of that was
originally covered with a wood plank floor where the roller
and slitter machines were located. The man at the rear is
standing on the stone base for the ovens and chimney.
Just north of the main building Robbins found a stone retaining wall with many top stones missing. He identified it as the west sidewall of a warehouse used in conjunction with the mill. The building had been forty feet long and thirty-two feet wide with three sides supported on flat stones spaced about ten feet apart. Closeby, southeast of the warehouse Robbins also found the remains of a small blacksmith forge that may have been used to repair and maintain mill equipment.
Robbins also identified the foundations of the mill company house:
'Some two-hundred and twenty feet northwesterly of the main mill building was located the "Mill Company HouseÓ. Its site was determined by the foundation stones and the abundance of chimney brick fragments and mortar. The Town of Dover map for 1831 places the ÒMill Company HouseÓ to the westerly side of the road to the Dover Union Iron Company. It stood upon the side of a hill, at a height considerably above the mill and the mill pond. It is likely that the heavy brush and trees growing today between the sites of the mill and the "Mill Company HouseÓ did not exist when the mill activity flourished. From the "Mill Company House" one could have gained a panorama view of the mill, the mill pond and the warehouse. Of course that was a century and some thirty odd years ago. Today one has to lay back the heavy brush to see but several feet in the direction of the old mill when they are standing upon the site of the "Mill Company House'.
The 'foundation stones and abundance of chimney brick fragments' mentioned by Robbins are no longer there. They may have been used to construct the riprap buttress to reinforce the bulging west wing of the dam after Robbins completed his work at the site.
Robbins report also described another stone foundation:
'Some distance southwesterly of the ÒMill Company HouseÓ, I should venture to guess that it would be some two-hundred feet, is located a foundation with three stone walls. In other words it 1s 1ike any foundation for a building, only one wall is missing. This kind of structure always suggests the site of a barn. There 1s no reason why we should think otherwise regardlng this evidence. Undoubtedly a barn stood there some years ago. There being no visible evidence of any other house in the vicinity, other than the "Mill Company House", we must go along with the conjecture that this barn was contemporary with the Dover Union Iron Company.It is reasonable to assume that the oxen, or other beasts of burden, were housed here.'
These walls are still visible at the site.
Robbins' report mentions another possible building near the mill:
'To the east of the main building was found the base
stones to an ell. This was possibly an office.
It may have been an auxiliary unit, It is unlikely that it played any part
in major production.'
The engineer's plan shows that the area was outlined with stones
when Robbins completed his work but these stones have since been removed.
Besides the section of waterwheel, Robbins found and recorded many other artifacts from the wheelpits, the working surface in the mill and the access area below the machines floor. William Gehling, an employee at Mill Farm, cleaned and restored many of these artifacts and each was identified with a key number and listed in an inventory.
Specimens include pieces of waterwheel spokes, boards from the bottom of wheel buckets, iron tie rods used to hold the waterwheel shrouds together, bearing rings for the waterwheel shaft axle, tongs, chisels, teeth broken from gears, metal roller shims and washers, a coupling casting, various other broken or damaged machine parts, used nails and bolts and assorted lengths of barrel hooping including one bundle of twenty-four hoops ready for shipment.
The gear teeth, roller shim specimens, coupling casting, finished hoops, nails and other worked metal strips are especially important in understanding how the mill was set up, how it operated and where the iron came from.
- - - - -
* - This bulging part of the dam eventually had to be reinforced by building a stone rip rap buttress similar to the one at the easterly bend in the dam. Today little original stonework is visible along this southwesterly wing of the dam.
Photographs Courtesy of the Thoreau Society, Lincoln, MA
8/9/00