wagons, have one tool-wagon precede and the other follow the train, while the forage has its position in the center; with this arrangement tools and cordage for temporary repairs are always at hand when wanted. a

Although Mr. Trowbridge's letter does not, perhaps, call for anything more, yet I have ventured to add the following suggestions derived from my experience in repairs, &c., at this depot, relating to material, &c.:

Pontoons: As refitted here are plated; that is, an iron plate of 3/6-inch iron and about 7 by 9 inches is screwed on over every butjoint; this is absolutely necessary to resist the strain of land transportation. b

Pontoon-wagons: I have fitted all these with whiffletrees by cutting off the projecting ends of the cross-bar with two lock-chains instead of one, and with hooks and chains for suspending the anchors to the side-rails, thus relieving the rear axle and bringing the weight nearly over the forward wheels, where it ought to rest. a

Officers in charge of trains during the recent movements, when these two improvements have just been tested, are unanimous in favor of both of them. I would also suggest that if new wagons are constructed they should be remodeled so as to admit of the introduction of an enever or double-tree in addition to the whiffletrees, thus relieving the wheel horses or mules of strain. a

Balk (longer common): I suggest that the balk and side-rail be made alike, or rather that the side-rail, as a separate piece, be abolished entirely. a While a side-rail will not make a balk without alteration, any balk will answer for a side-rail perfectly as it is, and whatever advantage may be derived from a difference in form is more than balanced by the loss of time in arranging them to load or build in the confusion if not previously arranged. In constructing here I am making all balk and no side-rail.

Balk (claw): In the absence of the Birago trestle or the canvas pontoon (when these are only required), the common long balk may be substituted in the abutment bays of a bridge by shortening and spiking or screwing in claws made of pieces of plank. a

Chess: The Y-pattern adopted here, and by which all new ones are made, is of 1 1/2-inch clear pin 13 feet long, with a shoulder 1 1/4-inches deep cut in each side and extending 2 feet from each end, with four rivets of 1/4-inch iron 12 inches and 10 1/2-inches long, one 1 inch from the end and one 1 inch from each shoulder, experience having proved that the rivet is required at the shoulder as much as at the end. c The width is imperatively required to be 12 inches.

Chess-wagons: As originally furnished were too tightly constructed in every part, and the system of locking very defective; until altered and remodeled at this depot none of them were capable of carrying even half an ordinary load.

Anchors: As hitherto furnished have weighed all the way from 60 to 140 pounds, while we have a number here, probably furnished for a larger bridge at Harper's Ferry, running from 500 to 850 pounds. I think that experience has proved that an anchor weighing much less than 100 pounds cannot be relied upon, and that much over this

a Approved.

b The planks on sides and bottom should in all cases run the whole length without buts, thereby dispensing with these plates.

c This is as previously ordered by me.