Presentation made at Bushy Run Battlefield Park June 12, 2010 BUSHY RUN BATTLEFIELD LOOKING FOR FORBES ROAD By William J. Johnson 1 and Donald W. Johnson 2 Abstract The Battle of Bushy Run is one of the most significant battles to have taken place during the Pontiac s War in Western Pennsylvania. A lingering question to some has been whether the Bushy Run Park is actually the battlefield. The map of the battle prepared by Thomas Hutchins in 1765 is a near perfect match to the topography of the park, but what if Thomas Hutchins did not go to the actual site of the battle when he prepared his map? The work undertaken by GAI Consultants to conduct archaeological studies at the park effectively has proved the site is the battlefield on the basis of military artifacts discovered in the ground. An additional confirmation that the park is the battlefield could also come through the location of Forbes Road, which is also mapped as passing through the battlefield. Geophysical surveying was undertaken at six areas that were suspected of crossing Forbes Road. In the eastern part of the site the mapped location of Forbes Road is also where there is a park track. In test areas across the exiting track, the results do indicate the presence of a road at a depth of about 1.5 2 feet, which does suggest an older road could be present beneath the current track, but the results do not conclusively say that this older road must be Forbes Road. Other theories as to the location of Forbes Road suggest the current highway next to the park could also easily be over Forbes Road, but the road would then probably have to loop into the park to go around a swampy area in the western part of the park. The geophysical results suggest this theory could also be correct, as there is the geophysical signature of a road going around the upper reaches of what would have been swamp and is now an auditorium. The possibility needs to be considered that both locations for Forbes Road are correct, but the actual road location migrated with time. The geophysical results do identify locations where Forbes Road could be present where additional archaeological excavations are warranted to provide verification. Historical Background The French and Indian War ended with the signing of the Treaty of Paris on February 10, 1763, but that did not end the conflict taking place in Western Pennsylvania. The Native Americans quickly realized that their rights were not a concern to either the defeated French or the conquering British. Under the leadership of Pontiac, the Chief of the Ottawas from the Detroit area, a loose federation of tribes from the Great Lakes, Ohio Country and Illinois Country began coordinated attacks against the British. In Western Pennsylvania Forts LeBoeuf, Venango, and Presque Isle were attacked and destroyed. In June of 1763, they began a siege of Fort Pitt and 1 D Appolonia (412) 856-9440 wjjohnson@dappolonia.com 2 Geophysical Consultant (612) 669-5317 www.archaeology-geophysics.com
sieges were also taking place at Forts Detroit and Niagara. This war became known as Pontiac s War. The turning point of Pontiac s War was the Battle of Bushy Run that took place on August 5 and 6, 1763, when Native Americans attacked a group of about 460 men led by Col. Henry Bouquet on their way to end the siege of Fort Pitt. Col. Bouquet and his men had just traveled 17 miles from Fort Ligonier and were approaching the Bushy Run Post where the men were to have obtained water and rested the night prior to the final push to Fort Pitt. Bushy Run Post was located on the South Fork of Forbes Road, rather than the original location of the road, as the original road was highly deteriorated. They expected resistance near Turtle Creek, but not where the attack took place on Edge Hill, just as they had made the turn on South Fork, about a mile east of the Bushy Run Post. The attack began at about one o'clock in the afternoon on August 5, 1763 by about 400 Native Americans (according to Bouquet s estimate), most probably coming from the siege of Fort Pitt, as the siege had been abandoned the previous day. Bouquet s tired troops suffered from a lack of water in the August heat and after a day where neither side had achieved a decisive victory they sustained heavy casualties. A makeshift shelter for the wounded was constructed with the large sacks of flour intended to be used as supplies for Fort Pitt. The next morning, again under heavy attack, Bouquet's men followed a tactic developed by the Native Americans and feigned a retreat, which lured the attackers into the open, subjecting them to bayonets and musket fire, leading to their rout. Fifty of Bouquet's men died and sixty were wounded at the Battle of Bushy Run. Bouquet continued on to Fort Pitt where he found the siege had ended the day before the battle and the fort was secured. The defeat at Bushy Run was the beginning of the end for the Native Americans in their war for independence. Is Bushy Run Park the Battlefield? What we know about the geography of the Bushy Run battlefield is from the field descriptions found in the journals of Col. Bouquet, as well as a detailed map made by Thomas Hutchins after the battle and published in 1765. 3 Thomas Hutchins was not personally at the Battle of Bushy Run, as records show he was a member of a court martial at Fort Pitt on August 4. His survey of the battlefield was made at a later date based on information provided to him. This map is a near perfect match to the modern topographic map of Bushy Run Park, as shown on Figure 1. Skeptics could argue that Hutchins actually went to the wrong place to make his map. He wasn t there, after all. That concept is dispelled by the findings made by the archaeological team from GAI Engineers and Consultants, who found original mid-18 th Century military artifacts on the property, some of which are shown on Figure 2. The inescapable conclusion is that the park is the battlefield. 3 PLAN OF THE BATTLE NEAR BUSHY-RUN gained by His Majesty's troops, commanded by Colonel Henry Bouquet over the Delaware, Shawanese, Mingoes, Wyandots, Mohikons, Miamies & Ottawas, on the 5th and 6th: of August, 1763. From an actual survey by Thos: Hutchins Assistant Engineer (1765) 2
Figure 1 - Portion of the 1765 battlefield map by Thomas Hutchins and a modern topographic map of Bushy Run Park the relationship of hills, drainage, and slopes is nearperfect. The question then becomes, what can a geophysical survey do to help with the interpretation of the battlefield? One unanswered question was the location of Forbes Road (South Fork), mapped by Hutchins as passing through the middle of the battlefield. 3
Locating Forbes Road Although clearly shown on the Hutchins map, a complicating factor to actually locating Forbes Road was that there is no guarantee that its position remained constant after the battle. Portions of Forbes Road constructed during the French and Indian War had already become unusable by 1763 and Bouquet preferred to use the newly constructed South Fork, effectively a shortcut to traveling along the original road. The location of this portion of the road could also have been modified as it was used for transport between Fort Pitt and Fort Ligonier. Farmers might also have modified the road with time. The basic starting point for locating Forbes Road was to take the Hutchins map as a starting point. Six areas were picked to intersect the mapped area Figure 2 - Some of many mid-18 th Century military artifacts found at Bushy Run Park by GAI of the road or where the topography of the land suggested a road might go. These areas were then surveyed with a range of geophysical techniques. Figure 3 Location of Forbes Road on a modern map with six geophysical survey blocks. Specifically, four techniques were used at Bushy Run Park: Geometrics G858 magnetometer operated in the vertical gradient mode. 4
DC resistance measurements using an RM15 resistance system manufactured by Geoscan Research with a multiplexer permitting data to be simultaneously collected from 2 different electrode spacings, 0.5 and 1.0 meters, the bigger the spacing the deeper the depth of penetration. Ground penetrating radar using a MALÅ Geoscience X3M radar system with a shielded 250 MHz antenna. Electromagnetic (EM) conductivity measurements with a Geonics EM-38 ground conductivity meter. The background for these techniques is beyond the scope of this discussion, but what the geophysics intends to provide are contrasts in soil characteristics, whose patterns can be interpreted based on their form. For example, roads usually show up as linear patterns. Typically, a road has a relatively high electrical resistivity (same as low conductivity) because of the greater degree of compaction of the road surface compared with surrounding soils and the fact that roads frequently have rocks added to the ground to increase their durability. Roads also are a disruption to the natural magnetic pattern of undisturbed soil observable by careful magnetic measurements, and this disruption is also often visible from ground penetrating radar (GPR) measurements. Figure 4 compares the geophysical results obtained over Block 1. An existing gravel track crossed Block 1 at 75N and this is evident in all sets of data, best resolved with the GPR at a depth of 1.5 feet. Strong responses in the magnetometer data cause by metal are located at Figure 4 Geophysical results from Block 1. 6E/89N, 14E/65N, and 35E/129N. Although the magnetometer responses are strong, there are no corresponding responses in the other methods so the conclusion is that the metal pieces are 5
not particularly large. The resistance data shows an area of low resistance. It is also seen in the conductivity data as an area of higher conductivity, and it is also apparent in the GPR data. Review of the GPR depth profiles indicates this area to be generally undisturbed so this feature is interpreted as natural soil conditions. At this location, the road anomalies correspond to the existing track, which is where Forbes Road would be expected to be present based on the historical map (Figure 3). Accordingly, all that the geophysics tells us is that a road can be interpreted only at the location of the existing track, which may also be the location of Forbes Road. Figure 5 Geophysical results from Block 2. The conditions identified from Block 2 are similar to those at Block 1 (Figure 5). The existing track is apparent is all data images, crossing the block at 75N, and is best resolved with the GPR to be present at a depth of 1.8 feet. A strong linear anomaly is also seen crossing the north end of the block. This is believed to be a water line. A weak linear anomaly is seen in the GPR image and in the 0.5-meter resistance image. Since it is more distinct in the 0.5-meter resistance data than in the 1-meter data, it is probably near surface (<0.5 meters). It is not seen in the magnetometer data or in the EM data. The cause is unknown, but may be an old path. It is not oriented in a direction that would suggest it is Forbes Road. Similar to Block 1, if Forbes Road is present within this block it corresponds to the existing track whose response may be masking any responses from the older road. Block 3 also crosses an existing track and is identified in Figure 6. A linear response seen in both the magnetometer and GPR images is south of and parallel to the track. It is assumed to be a utility line. A band of high resistance has been mapped in the southwest corner of the block. There are corresponding responses in the other methods, although faint. Review of the GPR depth profiles indicates that there is a buried surface at a depth of about 3 feet in this area. It may be a natural soil horizon, but because it is of limited extent, it may be cultural in origin. As further discussed in the conclusions, one theory made to us after our report was presented to GAI 6
is that Forbes Road followed current Bushy Run Road (Route 993) south of the park, but entered the park when it had to deviate around swampy ground associated with the stream in the western part of Figure 3. Block 3 therefore covers two possible locations for Forbes Road, one following the existing track and the other trending NW-SE in the southern part of the block. Figure 6 Geophysical results from Block 3. Block 4 is north of the amphitheater where no existing track crosses this block. A linear response is seen in the magnetometer data between about 113 and 119 North. It may be a small utility line that crosses the site or an old path no longer visible on the surface. In any case the linear feature appears to be too narrow to be a road. The most distinctive feature of the resistance and conductivity data is the higher resistance, lower conductivity zone, in the southeast corner. It could be natural soil variation, but could also be where Forbes Road deviated around swampy ground, consistent with the concept described for Block 3. Block 5 was located to cross a flat area on the hillside that could also have been a candidate for the location of Forbes Road if the road followed a higher bench than shown on the Hutchins map (Figure 8). The most distinctive feature in the geophysical data is a gently curved linear feature crossing the block from the northeast corner to the middle of the west side. It is seen distinctly in the 0.5 meter resistance data, but poorly in the 1-meter data indicating that the cause is shallow. It is poorly seen in the conductivity data probably because the feature is nearly parallel to the transect direction and because the weeds, although cut, required that the instrument be held a little higher off the ground. It may be a path or small road going up the hill from the amphitheater. 7
Figure 7 Geophysical results from Block 4. Figure 8 Geophysical results from Block 5. Block 6 (Figure 9) is possibly the most interesting of the survey blocks, since Forbes Road would be expected to pass through this area, regardless if the road is as mapped by Hutchins or followed Bushy Run Road and deviated around swampy ground. In this area there is no modern track that could interfere with the interpretation. An area of high resistance (low conductivity) crosses the center of Block 6. It corresponds to the anticipated orientation of Forbes Road but is 8
wider than the road would be expected to be. It should be noted that old dirt roads did not always follow the same tracks to avoid areas where the tracks were deep or muddy, for example, and the effective width of the road would become wide over time. There is a weak band seen in the GPR data that corresponds to the east part of the resistance high. This has a width that more closely corresponds to a road, and if due to a road, may indicate the portion last used. It should be noted that this anomalous area is located approximately where the historical map shows Forbes Road to be present. Figure 9 Geophysical results from Block 6. Conclusions and Observations Bushy Run Park is certainly the site of the battlefield. This is demonstrated by the excellent correlation of the battlefield map by Thomas Hutchins with modern topography, but also from the period military artifacts found by GAI. The problem of locating the South Fork of Forbes Road through the park is not so easy to solve, however. The geophysical surveying has detected the presence of roads. What the geophysical surveying cannot answer is when the roads were constructed or in the areas where an existing track is not present, if the geophysics is actually detecting an old road. Figure 10 presents two possible interpretations of the geophysical results. In the eastern part of the site the mapped location of Forbes Road is also where there is a park track. In test areas across the exiting track, the results do indicate the presence of a road at a depth of about 1.5 to 2 feet, which does suggest an older road could be present beneath the current track, but the results do not conclusively say that this older road must be Forbes Road. Other theories as to the location of Forbes Road suggest the current highway next to the park (Bushy Run Road Route 993) could also be over Forbes Road, but the road would then probably have to loop into the park to go around a swampy area in the western part of the park. The geophysical results suggest this theory could also be correct, as there is the geophysical signature of a road going 9
around the upper reaches of what would have been swamp and is now an auditorium. The possibility needs to be considered that both locations for Forbes Road are correct, but the actual road location migrated with time. The geophysical results do identify locations where Forbes Road could be present where additional archaeological excavations are warranted to provide verification. Figure 10 Different interpretations of results 10