On January 25, 1864, Brigadier-General Henry W. Benham, commanding the Engineer Brigade of the Army of the Potomac, completed a lengthy report for Brigadier-General Joseph G. Totten, the Chief Engineer of the US Army. The report touched upon several subjects, but largely concentrated on improvements to bridging techniques then in use. This was not a new round of correspondence. Benham wrote a similarly lengthy and detailed letter to Totten in November 1863, discussing changes in the drill for pontoon bridging.
The reports, including enclosures from subordinate officers, include over fifteen pages total in the printed OR. Far too much for a single blog post. So I might examine in fine detail at another date. Feel free to browse the November 1863 letter or the January 1864 report if I don’t get to that examination in short order. I suspect a detailed examination would elicit a long sigh at the discussion anchor bolts, abutment sills, and claw-balks. So let me focus on something less “engineer-y” and perhaps a bit into the historiography side of things. At the end of his November letter, Benham mentioned some photographs sent along with the correspondence:
I have the pleasure of inclosing you, for the further explanation of the method of laying these bridges, some photographic views taken during the progress of construction.
No. 1 shows the pontoons ready with the material, and the boat squads ready for the construction (at foot of East Fifteenth street).
No. 2 shows the progress of construction of the raft after four to five minutes’ labor.
No. 3 shows the progress of the bridge raft after six to seven minutes’ labor.
No. 4 shows the bridge completed, with the bridge squads formed ready to march off. Parts of a trestle and canvas pontoon bridge across a cove along the shore are in view here.
No. 5 shows, from a nearer point of view, the pontoon bridge ready for service.
No. 6 gives the view down the Eastern Branch with pontoon bridge to beyond Navy-Yard Bridge, and oarsmen having oars raised ready to move the bridge for dismantling. Parts of pontoon balk-head used for laying the bridge raft are shown in foreground as it was placed to save the men from the water, though rather delaying than expediting the work. (emphasis added)
Believing that they would also be interesting at the Department, I have also added two other photographic views.
No. 7, showing the old or generally practiced method of laying bridges by successive pontoons.
No. 8, a view of the pontoon bridges laid by the engineer brigade under my command on the morning of April 29, 1863, at Franklin’s Crossing, 2½ miles below Fredericksburg. This shows in the distance the ruins of the villa of Mansfield, the site of General Bayard’s death.
Photo “No. 8″ referenced by Benham may be one of those examined by John Hennessy and Eric Mink in 2011. Of the others described (or is it “captioned”) by Benham, I’ve found no direct matches. However this photo from the Library of Congress collection is a close match to “No. 6″:
This shows two pontoon bridges across the Anacostia River, looking from the Navy Yard. Lots of neat stuff to discuss in this photo. But for today, let’s just consider this as establishing Benham’s practice of using photographs to support his suggestion (and I bet Benham would have loved PowerPoint!).
That in mind, consider a section from the January 25, 1864 report:
The modification I propose (of which I inclose sketch) in the French pontoon is to take off 3 feet in length from the bow and 2 feet from the stern, while the “floor” remains of the same length, the ends to the depth of one plank downward to be of a thick plank or timber, with a shield or bunter which should slope about 3 inches outward.
Benham went on to say this modification would prevent some of the damage to the pontoons while on the march and make handling much easier. Here’s the line drawing included with the report:
Fairly typical comparison diagram, using dotted lines to demonstrate the differences between the original and proposed modification. Probably sufficient to demonstrate the particulars for an engineer of Totten’s experience. But what do they say – “A picture is worth a thousand words”? How about this picture, might it offer a thousand words comparing two types of pontoons?
Notice the difference between these two pontoons, particularly at the bow end. While not precisely matching the dashed lines in Benham’s drawing, the pontoon on the right is close to his proposed modification. Was this a photograph taken for the benefit of Benhan to demonstrate his suggested changes?
Working against my suggestion, the Library of Congress record for this photo does not provide a location. The original caption on the back of the stero-view card does not mention any special nature of the two boats:
This view shows two of the boats (of which the army bridge is made) on wheels ready for the march. Each pontoon wagon is drawn by six mules. These pontoons were always getting stuck in the mud, and the soldiers, struggling along under their own burdens, were obliged to haul on the drag ropes, and raise the blockade. Probably no soldier will see this view without being reminded of the time when he helped to pull these pontoons out of the mud, and comforted himself by searing at the mules.
Doesn’t sound as if this photograph captured a comparison of two type of pontoons. Maybe the studio felt the public would not appreciate the comparison, and thus offered a “pedestrian” caption.
However there are several other views of pontoons dated to the winter of 1864, taken at the Engineer Brigade camp at Rappahannock Station. And some seem ready made for a comparison of the two types. This photo carries the Library of Congress caption “Pontoon wagon and boat, 50th New York Engineers, Rappahannock (i.e. Brandy) Station, Va., March, (i.e. Feb.) 1864.”:
So the right time and place. And this appears to be a standard “French Pontoon.”
Compare to this photo, also citing the 50th New York Engineer camp at Rappahannock Station in March 1864:
If not an exact match for Benham’s drawing, it does look like the pontoon on the right side of the photo above. And another photo must have captured the same (or similar) boat from the front:
With more of these in the background… see them?
There’s even a photograph of a wagon without the pontoon:
And let’s not forget the canvas pontoon:
That photo, in particular, just stands out as if tailor made for illustrating some manual. The men are in the background, not the foreground. The subject here is the equipment, not the personnel. These pontoon photos are like some “walk around” we would use today to demonstrate the particulars of a piece of equipment.
Maybe the photographer was just hanging out with the engineers taking in shots of the equipment. But this is not some point-and-shoot camera we are talking about. These were expensive (relatively speaking) glass plate photos. So why waste a plate on some static equipment displays? On the other hand, perhaps these and similar photos taken at the 50th New York Engineer camp were intended to help Benham illustrate his reports.
Something I’ve learned over the years – when studying Civil War photographs, it is just as important to know the “why” story as the “what” of the subject.