The 1779 Erskine Map includes a meticulously drawn sketch of the Howell's Ferry operation served by Lower Ferry Road on the New Jersey side of the Delaware River. If you had Erskine's map and were familiar with the overall road network including "Old River Road" (Sullivan's Way) you could tell at a glance that the ferry being shown by Erskine was indeed located down near today's railroad and not thousands of feet upriver at Wilburtha or Upper Ferry Roads.
It would be possible to translate the "you could tell at a glance" into actual numbers measured in feet, by setting up a ratio between two distances both measured on the Erskine map, "Distance 1" being a SHORT distance measured somewhere inside the ferry sketch, and "Distance 2" being a LONG distance measured along "Old River Road" (between Lower and Upper Ferry Roads). Sample calculation: 0.12-inches (creek to cable)/1.1-inches (Old River Rd). Now on the 1882 map there is a scale which allowed me to determine that 1.0-inch on the map equals 1,320-feet on the ground. Sample calculation: 4.8-inches measured along Old River Road (between Lower and Upper Ferry Roads) x 1,320 equals 6,336-feet (slightly more than by odometer). Final calculation: Creek to cable = (0.12-in/1.1-in) x 6,336 feet = 691-feet. This method combined with other information collected on the ground has long term potential but in the short term is problematic. However, based on the reported and apparent accuracy of Erskine's work, a quick and easy approach is to assume his distances and angle measurements are accurate and solve it graphically.
Graphics Procedure:| Initial Trial Method: A precise enlargement of the Erskine sketch was traced onto clear plastic. I held the plastic above and parallel to the 1882 map and it looked like they matched. | |
| Final Method Used: The two images were brought to the precise same scale, by starting with a high resolution image of the 1882 map and using the ability of the HTML image command to reduce the image one increment at a time until the two images were brought to the exact identical same scale. This time by holding the plastic overlay against the computer screen the road networks matched in both the N-S and E-W directions, and I was able to transfer Erskine's 1) ferry sketch, 2) Lower Ferry Road, and 3) "Old River Road" onto the 1882 map. |
Erskine's 1779 Survey + Breou's 1882 Map
Howell's Ferry Crossing at Lower Ferry Road on the New Jersey side of the Delaware River
Return to Susan Taylor Letter
GOTO Letters Index