Category Archives: Technology

Understanding Milling Terms

Inside the Chapman - Beverley Mill (circa 1990)

Inside the Chapman – Beverley Mill (circa 1990)

As with all industries, Milling brings with it a host of technical terms that may or may not be familiar to the average person.  Some terms are straight forward having meanings that are fairly obvious . . .

Grain hopper: a hopper above the vat which holds the grain to be milled

Meanwhile others are a little trickier. For instance, you might assume that a ‘Mill bill’ is a statement that notes what a patron owes the Mill, but actually it is defined as ‘a chisel ended tool used for dressing or sharpening the grinding surface of a millstone.’  Here are a few of our favorite tricky terms:

Shroud: the rim of a water wheel which forms the sides of the bucket enclosures.

Shoe: a tapered trough that feeds grain into the eye of the runner stone for grinding and then between the two millstones.

Eye: the center hole in a millstone

Dresser: a person who works on the millstone furrows.  Also a name for the machine that bolts or sifts flour.

Read more Milling terms  HERE  and even more HERE!

Turning Water Into Power: Water Wheels


An Up-close View of the Chapman – Beverley Mill Water Wheel .

The Chapman – Beverley Mill used a 30 foot overshot water wheel to power its millstones.  But what does that mean?

The following text explains how an overshot water wheel works and the advantages of using this type of wheel.  To read the full article including this and other kinds of water wheels, Click Here.
overshot waterwheel design

The Overshot Water Wheel Design is the most common type of waterwheel design. The overshot waterwheel is more complicated in its construction and design than the previous undershot waterwheel as it uses buckets or small compartments to both catch and hold the water.

These buckets fill with water flowing in at the top of the wheel. The gravitational weight of the water in the full buckets causes the wheel to rotate around its central axis as the empty buckets on the other side of the wheel become lighter.

This type of water wheel uses gravity to improve output as well as the water itself, thus overshot waterwheels are much more efficient than undershot designs as almost all of the water and its weight is being used to produce output power. However as before, the waters energy is used only once to rotate the wheel, after which it flows away with the rest of the water.

Overshot waterwheels are suspended above a river or stream and are generally built on the sides of hills providing a water supply from above with a low head (the vertical distance between the water at the top and the river or stream below) of between 5-to-20 metres. A small dam or weir can be constructed and used to both channel and increase the speed of the water to the top of the wheel giving it more energy but it is the volume of water rather than its speed which helps rotate the wheel.

Generally, overshot waterwheels are built as large as possible to give the greatest possible head distance for the gravitational weight of the water to rotate the wheel. However, large diameter waterwheels are more complicated and expensive to construct due to the weight of the wheel and water.

When the individual buckets are filled with water, the gravitational weight of the water causes the wheel to rotate in the direction of the flow of water. As the angle of rotation gets nearer to the bottom of the wheel, the water inside the bucket empties out into the river or stream below, but the weight of the buckets rotating behind it causes the wheel to continue with its rotational speed. The empty bucket continues around the rotating wheel until it gets back up to the top again ready to be filled with more water and the cycle repeats. One of the disadvantages of an overshot waterwheel design is that the water is only used once as it flows over the wheel.

Rediscovered Photos Shine Light On Milling Operations

Recently, we were excited to find quite a few references to the Mill in the Prince William County Photo Archives.  Housed in the Bull Run Regional Library’s Ruth E. Lloyd Information Center (RELIC), there were over two dozen images of the Mill inside and out that we had never seen before.  The great folks at RELIC kindly scanned the photos – some of which we have included below.

The images, largely taken by Henry H. Douglas in the latter part of the 20th Century, provide a wonderful opportunity for us to better understand how the Chapman – Beverley Mill once operated.

Beverley Mill and the ‘Plaster Industry’

"Beverley Mill in 1938."

“Beverley Mill in 1938.”

In October 1981, Henry H. Douglas published an article in “Northern Virginia Heritage” titled simply “Beverley Mill” which featured the history of the Mill. In the following excerpt, Douglas discusses how and why the Mill was used to grind plaster in the years leading up to and following the Civil War.

As the mill was rebuilt [following an 1858 fire], new machinery was installed, probably for plaster grinding.  The mill may well have been used as a plaster mill as well as a grist mill. A plaster mill grinds crushed gypsum into ‘plaster’ or ‘lime’ for use as a fertilizer and soil conditioner.  This development was doubtless due to the opening of more and more farm land in Northern Virginia, and to the advent of the railroad to handle the heavier hauling that was part of the ‘plaster’ industry.

Where did the gypsum come from? Some have said that it came by boat from Nova Scotia to Alexandria, and by train from there.  A much more likely explanation was provided by Robert Beverley Herbert of Avenel, near The Plains, grandson of the first Beverley to be connected with the mill.  He said that his cousins, Robert and Bradshaw Beverley, operated a quarry in the Gap where they crushed stone.  They also quarried near Winchester in the Shenandoah Valley.  He always thought they shipped the gypsum from Front Royal on the railroad  After quarrying, it was crushed into pieces not more than 1/2″ in diameter.  At some point, either at the quarry of near the mill, it was subjected to intense heat to ease the  final grinding process.

Douglas’ full article can be found online.  Click here to read more.

Preservation Versus Restoration: What’s the Future of the Mill?

An arsonist's fire left the Mill in ruins and TTMAC with a choice: Preservation, Conservation or Restoration.

An arsonist’s fire left the Mill in ruins and TTMAC with a choice: Preservation, Conservation or Restoration.

Shortly after the devastating 1998 arson that gutted the historic Chapman – Beverley Mill, members of the Turn the Mill Around Campaign had to make a decision.  With the Mill now in ruins, what would be the aim of the organization – to conserve, preserve or restore the Mill?  After speaking with structural engineers and finding that restoration was impossible due to the weakened state of the stone in the walls, TTMAC embarked on an effort to conserve and then preserve the Mill in its ruined state.  But what does that all mean?

Read Karen Kroslowitz’s article ‘Preservation, Conservation, Restoration: What’s the Difference?’ for definitions of each term.

Here at the Mill, the stabilization of the structure’s walls, completed in 2006, is like a form of interventive conservation.  The goal of the internal anchoring system is simply to mitigate the existing damage and to enable the Mill’s walls to safely stand without further stone loss.

The lead sheeting that you see on the Mill’s windowsills is a form of preventive preservation.  Its function is to prevent water from seeping into the walls, the freezing and thawing of which would result in additional stone fracturing.

While the Mill will never be restored to its former glory, it remains preserved as a testament to Northern Virginia’s agricultural history.

Keeping the Mill’s Walls Standing


Stabilizing the Chapman – Beverley Mill Walls


Turn the Mill Around Campaign faced a very big problem when it took over management of the Mill in 1998. The fire that year had left the walls of the structure fragile and in danger of collapse.  TTMAC contacted numerous companies about stabilizing the ruins, but each considered the walls too delicate to save.

Workers Installing Cintec Anchors

Workers Installing Cintec Anchors

Finally, TTMAC contacted Cintec, a preservation business known for stabilizing European castle ruins. Cintec devised a plan to strengthen the walls one at a time. Beginning on the South wall (the most fragile), Cintec workers drilled down through the wall from top to bottom inserting a strengthening rod and filling the void with a mortar-like substance.  The South wall was completed in 2004 and by 2006 the whole structure had undergone the Cintec internal anchoring system process!

For an in-depth explanation of how Cintec anchors work and how they’re installed, take a look at the stabilization of the Baltimore Basilica.

Inside a 19th Century Mill


Aldie Mill built circa 1807

Over 270 years after the Chapman – Beverley Mill was constructed there is still much to be learned about the structure.  Photos taken inside the building before the 1998 fire give us the best clues as to how the mill ground grain, but studying the inner workings of other mills in the area is also helpful.  Nearby Aldie Mill, built around the turn of the 19th Century, provides us with a great idea of how mills of this era worked.  Take a look at this video to see Aldie at work!