How many times have you read or heard that expression? Yes, throwing up works. As if some powerful entity stands in front of the lines and with some hand motion moves the earth into the nice geometrical alignment that forms the precisely planned fortification. That’s not how it works when making works. Nay, someone has to use the shovel to pile that dirt up to the desired heights and contours.
That said, have you ever tried to pile earth up to a specific height and shape? How’d that play out? One might just start digging, then go back and measure the progress. Of course that would lead to a lot of re-work and adjustments. A better approach would be to have some stake or mark in place that sets the extents of the dirt pile and the desired height. Sort of a “practical” approach to the dirt piling, if you will, by marking and setting the particulars on the ground.
Mahan detailed just such a practical approach under the chapter title “Manner of Throwing Up a Work.”:
The foregoing chapters contain all that is requisite to determine the plan and relief of field works under all circumstances of variety of ground. To follow a natural order, the next steps will be to describe the manner of laying the work out on the field, which is termed profiling; the distribution of the workmen to excavate the ditch, and form the parapet; and the precautions to be observed in the construction.
So three steps here in the actual construction – project the plan onto the ground, divvy up the labor, and address particulars in the construction. We’ll look specifically at that first part in this post. For all the paper, ink, and brain-cycles spent developing the “plan” – tenants of which we’ve discussed at length in earlier posts – nothing matters until the works are actually constructed to the specifications. A perfect plan can be undone by someone shorting a half-foot on the height of the parapet or making a narrow banquette. So these particulars must be precisely related to the men working with the shovels. This is how that is done:
Poles having been planted at the angles of the work, and the height of the interior crest marked on them, a line is traced on the ground, with a pick, showing the direction of the interior crests.
My lack of artistic talent aside, that would look something like this:
We have the stakes, in green, at the angles of the desired work – in this case a simple lunette. A red hash mark indicates the desired height of the interior crest. And a dark blue line, nicely showing the faces and flanks required, represents the line traced by the pick. Those in place, the next step:
At suitable distances, say from twenty to thirty yards apart, cords are stretched between two stout pickets, in a direction perpendicular to the line marked out by the pick; these cords should be exactly horizontal. A stout picket is driven firmly into the ground, where the cord crosses the pick-line, and a slip of pine, on which the height of the interior crest is marked, is nailed to the picket.
Which would look something like this:
For clarity I’ve only depicted the work on one face here. We have the perpendicular cords in yellow. At the intersection of the cords and the pick-line, there are green pickets with the desired red hash marks for the height of the interior crest. That accomplished, we continue:
The thickness of the parapet is measured on the cord, and a picket driven into the ground to mark the point. The base of the interior slope, and the tread of the banquette, are set off in a similar manner; and a slip of deal is nailed to each of the pickets.
So we add more pickets….
Note, I’m adding an additional line that Mahan did not mention. The interior blue line depicts a measure back along the cord for placement of the second set of pickets. If I were doing this on the ground, I’d have a second pick-line as sort of a “measure twice” validation. But regardless of how it is determined, we have a second row of pickets (green, again) with a hash mark for the desired height of the banquette tread.
The height of the interior crest, and the tread of the banquette, are easily ascertained, from the position of the cord, and the interior crest; these points having been marked on their respective slips, the outline of the parapet is shown by connecting them by other slips, which are nailed to the uprights; the banquette slope, and exterior slope, will be determined by a similar process.
That results in this, Figure 18 from Plate II in Mahan’s Treatise:
We’d see a structure like this placed along every one of the yellow cord lines of my diagram. With one of these placed about every 20 to 30 yards, there’s a standing reference for those piling the dirt.
From the profiles thus formed perpendicular to the interior crests, the oblique profiles at the angles can readily be set up, by a process which will suggest itself without explanation.
Honestly, I do wish Mahan elaborated more on the obliques at the angles. But the manner that comes to mind is simply “smoothing” and adjusting the points where the two lines meet to form the angle. Basically, a beveled “cut” to each side where they join. Sort of getting a giant miter box out, I’m at a loss to display that here.
Having completed the profiling, the foot of the banquette, and that of the exterior slope, are marked out with the pick, and also the crests of the scarp and counterscarp. All the arrangements preparatory to commencing the excavation are now complete.
Yes, what he said… and start digging…. Well, we’ll wait until next week to start that, OK?
(Citations from Dennis Hart Mahan, A Treatise on Field Fortifications, New York: John Wiley, 1852, pages 32-33.)