NOTE Numbers 10.
In the siege operations herein considered, filled sand-bags have been used for the following purposes: Rivetting parapets and embrasures, forming loop-holes for sharpshooters, filling gabions, foundations for mortar platforms, coverings for splinter-proofs and magazines, and making banquette treads and traverses. The bags have also been used for transporting sand and shell by hand.
It is hard to conceive how this siege could have been conducted without sand-bags. Forty-six thousand one hundred and seventy-five, according to the account kept at the engineer depot, have been expended on the portion of the work herein described.
In the construction of the batteries against Fort Pulaski, which were also built of sand, but few sand-bags were used. Only a small portion of that work, however, was executed under fire.
The material of the bags here used was a good quality of gunny cloth, although rather light for some of the purposes for which the bags were used. They were sewed with cotton twine. The first lot furnished had the chain-stitch; the later ones, the lock-stitch. The latter is far the best. Each bag contains .63 of a square yard of cloth, and, when finished, weights 6 1/8 ounces.
The dimensions of the filled sand-bags, when laid, varied from 6 by 10 by 24 inches to 5 1/2 by 11 by 23 inches, and contained .85 of a cubic foot of damp sand, weighing about 85 pounds; hence 32 to the cubic yard.
The bags were always laid as headers and stretchers, and usually in the English or Femish bond.
Our experience proves that sand-bags which are tied before being laid should not be more than three-fourths filled. If full, they do not lay as well, and are more liable to burst on becoming wet or under great pressure. It is more rapid, but less economical, not to tie the bags at all, but give the throat a twist, and turn it under the end of the bag as each is laid.
Sand-bag rivetting requires less anchoring to make it stand than any other. Of the rivetting herein described, only that of the heavy guns was anchored by means of wires and pickets. Scarcely any of the portions not anchored failed for want of it. In the siege of Fort Pulaski, much of the hurdle and fascine rivetting gave out because not properly anchored. If the sand-bag rivetting of a battery which is being fought is kept wet, the sand will not so readily escape through the rents in the bags, nor will the bags burn. But this dampness hastens their decay.
At the end of two months the sand-bags used in rivetting the siege works herein described began to show signs of decay; but with careful usage, under favorable circumstances, sand-bags might not require replacing in twice the above time.
Abrasion, the result of serving guns, and from other causes, made holes in the bags, which allowed the dry sand to escape, thus destroying the rivetting. When the interior space would admit, sand-bag rivetting which had thus failed was repaired by facing it with a sod wall.