01/03/2010 Slide Presentation for SHA 2010 by Dan Sivilich
"HEAR THE CANNONS ROAR! 20 Years of Metal Detecting at a Troaini painting
Revolutionary War Site." Or … Electronic Archaeology at Monmouth
Battlefield State Park, Freehold/Manalapan, NJ.
20 years of metal detecting at Monmouth Battlefield State Park has GIS map of Ordnance at
yielded several thousand military artifacts, but when will this cultural Monmouth
resource be depleted?
As most of us are aware, the concept of battlefield archaeology was 2 Bighorn Photos
developed in 1984 at the Little Bighorn National Monument when, due
to a number of factors, Doug Scott chose to enlist the assistance of
metal detecting volunteers.
Since that time, metal detectors have become the tool of choice at BRAVO -Cooch's Bridge 1
nearly all large-area military sites.
As shown in this table compiled by Jo Balicki, the number of artifacts Shovel test table
found using metal detectors at MILITARY SITES is significantly
greater than classical shovel testing. I particularly like the data for
Antietem: 2 artifacts found in shovel tests and 1679 by metal detectors
and Manassas: shovel tests - 3 and metal detectors - 1698.
The Battle of Monmouth took place on June 28, 1778 in Freehold, NJ. Molly's Locations
It was the largest and longest land battle of the Revolutionary War.
Early research of the accounts of the Battle were based on inaccurate
maps and sketchy details. As a result, interpretations were confusing
and off by as much as a half of a mile. There are still 7 locations
marked for Molly Pitcher's "well" or spring. All of them are wrong!
Looking at the 2 locations that are still most frequented by visitors. Molly GIS
CLICK TO ANIMATE
There is also the controversial meeting between General Washington
and his second in command, General Charles Lee. Lee's men were
retreating in a disorderly fashion when it is reported that Washington
met Lee at the Causeway Bridge and scolded him and sent him to the
rear. For decades a brass plaque on a granite boulder marked this
historic meeting location. However, archaeology has identified the
correct causeway bridge.
CLICK TO ANIMATE
The stone marker has been removed.
In 1987 I began metal detecting a farm field in Freehold that was BRAVO metal detecting
owned by Bell labs and was slated for destruction. I accidentally found
one of the largest conflict areas of the Battle of Monmouth. In 1990
members of BRAVO began systematic metal detecting surveys of the
state park and continue to do so now. In those 20 years, the Battle of
Monmouth has become the most accurately documented and
interpreted battle of the Revolutionary War. Because of this
documentation, the farm on which I originally discovered a large
segment of the battle was ultimately purchased by the State of NJ and is
now part of Monmouth Battlefield State Park.
That area has been in continuous agricultural use. It has been metal Belle Terre chart
detected nearly every year after it is plowed and every year more
artifacts are found. The number of artifacts appears to be diminishing,
but not completely. Note: some of the spikes are due to more field days
than in other years.
After years of intense metal detecting, why do we continue to find Adrian with musket ball
artifacts at this site?
Metal detectors primarily work by sending a very low frequency
microwave into the ground. When this wave encounters an object,
some if it is absorbed and some of it is reflected back to a receiver in
the coil. This data is analyzed and the type of object and its depth is
displayed on a screen to the operator. Most detectors only have a range
of 8 - 12" depending on the size and mass of the target. The microwave
transmission field is a diminishing cone. The further away the target is
from the coil, the less chance of finding it. One's natural instinct is to
sweep courses the width of your coil, typically 8 1/2", but you are
actually only covering a 2 - 4" swath for deeper targets.
However, the probability of recovering more artifacts can be increased
by bringing the coil and artifacts closer to each other.
In wooded areas such as the Washington Chapel site at Valley Forge, Leaves at VF
this can be done by removing the build up of leaves and humus.
The simple removal of the leaves significantly increased our artifact Adrian and Ed
Additional plowing of agricultural areas causes more artifacts to move BRAVO at the Sutfin Orchard
vertically into the detector depth.
Proper identification of artifacts is the most important step in the Round musket balls
process of analyzing and interpreting a site. Areas of conflict are
usually identified by the ordnance that is excavated. One of the most
prolific at Revolutionary War sites are musket balls. Lead musket balls
come in a variety of diameters.
The diameter of a musket ball can be used to identify what weapon it Musket ball chart
came from based on the bore size.
But how do you measure the diameter of a non spherical musket ball 4 impacted musket balls
that hit some thing or some one?
If the diameter cannot be measured directly, it can be calculated from Sivilich Formula
the gram weight of the artifact. Archaeology at Monmouth was
directly responsible for the development of the Sivilich Formula:
Diameter in inches = 0.223204 x (Weight in grams)1/3
Hint for non-math people: this is a cube root.
Daniel M. Sivilich, 1996 “Analyzing Musket Balls to Interpret
a Revolutionary War Site”, Historical Archaeology 30(2):101-109.
It is most important to identify artifacts correctly. When we first found Canister shot
2 musket balls fused together, we thought we had a very rare artifact of
a British musket ball and an American musket ball that had collided in
mid air and fused together. After excavating numerous specimens, we
realized that we had lead canister shot that was fused together.
Canister shot is a tin can filled with lead balls. Polish canister
It is fired at the ground in a glancing angle about 75 yards in front of Me and Motts
The can skips off the ground and ruptures from the force of impact and Dead British
the shot rips through the enemy ranks. This is a very effective anti-
The extreme force of the can hitting the ground compresses the Square and wedge canister
contents violently. This compression caused some of the balls to fuse
together. Other lead balls get concave depressions from neighboring
balls and take wedge and square shapes.
The Battle of Monmouth was the site of the largest land artillery duels Artillery in smoke
of the Revolutionary War. It is estimated that over 3000 cannon balls
were fired by the 14 American and 10 British cannons that were
engaged for over 2 1/2 hours.
Literally thousands of military artifacts have been excavated at GIS - All military artifacts balls
Monmouth in the past 20 years. at Monmouth.
However, only 5 cannon balls have been found. Where are the other GIS - cannon balls at
GONE - stolen by relic hunters. People have been walking the Treasure magazine
battlefield for decades looking for them. In the late 1800's after the
railroad came to Freehold, local farmers would advertise in New York
and New Jersey papers, inviting people to relic hunt their farms and
buy fruit and vegetables in the process. It's only one cannon ball - what
can be the harm? Here is a copy of Treasure Magazine from the early
1970's. Notice the map of the Battle of Monmouth.
Here is a sketch based on a turn-of-the-century stereoscopic photograph MCHA Lockwood sketch
located in the Monmouth County Historical Association of a local relic
hunter's collection. Notice the British stirrup! These artifacts are
nowhere to be found today.
This is a tree section currently at the Monmouth County Historical MCHA Tree
Association with a 12 pound cannon ball and British Howitzer shell
fragments, most likely cut down as a souvenir in the 19th century.
MCHA has boxes of cannon balls donated by locals whose
grandfather's found them while farming. Their exact locations have
NEVER been recorded. Therefore, they are virtually useless for our
battle analysis. We have lost the ability to interpret the most significant
artillery battle of the Rev War. Or have we?
Looking at one segment of the Battle of Monmouth, we know the Perrine Ridge
American artillery is somewhere in this vicinity.
By examining historical documents, such as the Michele Captain du Cheznoy map with flying
Cheznoy map - cartographer to the Marquis de Layfayette circles
Looking at the incoming British Howitzer fragments, we can accurately Perrine 2
locate the American Artillery line
Using this information, we can map the American artillery ordnance Perrine 3
and identify the location of the Sutphin orchard in which the Scottish
Highland 42nd Regiment of Foot got trapped and fired upon with deadly
The archaeology of Monmouth has even discovered before unknown Perrine 4
segments of the battle. For decades historians have taught us that the
Crown Forces never crossed the causeway bridge. Our data shows the
contrary. Both the recovered American artillery ordnance and musket
balls (not shown in this slide), show concentrated fire on the northwest
side of the bridge. Surely they were not firing at gophers, but British
troops who crossed the bridge.
In another segment of the battle, we have been able to locate the Combs 1
position of 4 French cannons, commanded by General Nathaniel
Greene, that fired into the ranks of the British Grenadiers and 33rd
Regiment of Foot as they were attacking Anthony Wayne and his
Pennsylvania regiments at the Parsonage farm. What is most
significant about this data is that we did not know the types of ordnance
used by these cannons. It was always assumed that they were using
cannon balls. Here we see the use of mixed case shot, lead musket
balls and iron grape shot balls packed in a tin can and fired at a distance
of about 600 yards!
Unfortunately a very important segment of the Battle of Monmouth has Motts on Howitzer
been lost. We do not definitively know the exact location of the 10
British cannons and 2 British 5 1/2" Howitzers. A sampling of those
missing 2,995 cannon balls may have given us a better picture of the
great artillery duel. They have been stolen by looters and we have been
robbed of a significant portion of Revolutionary War history.
But the detecting and digging still goes on. This is a small solid gold Gold cuff link
sleeve link just found November 28, 2009 at the Parsonage site - the
site of the British Grenadiers and 33rd Foot. Note: just another
advantage of using metal detectors - this was small enough that it could
have possibly fallen through a standard 1/4" mesh screen used in
Back to the original question - when will the military artifacts at
Monmouth be depleted? I don't know - ask my daughter of the
University of South Florida or Carin Boone of Temple University, and
the next generation of military archaeologists. Surely the work will
continue long after I am gone.
This has been a BRAVO presentation! Thank you.