Redoubt Donaldson (now called W. D. Whipple) is situated midway between Hyde Ferry Fort and Gillem. It is a small battery with seven exterior and two interior embrasures. On the gorge, closed by a stockade, is a little octagonal block-house of ten feet sides, made bomb-proof. This small redoubt, intended for a six-gun field battery, covers the ground between Gillem and Hyde Ferry Fort, and is supported by infantry entrenchments on either side. I devised it for a model battery. The faces from angles of 144 degrees, while the embrasures open 40 degrees, so that the guns on each face can fire parallel to the contiguous capitals. By this arrangement there are no sectors without fire; in fact, the fire on the bisecting line of the angles is equal to that in any other direction. Such batteries, placed at intervals of 600 yards along infantry entrenchments, constitute a good defensive line for inclosing a city. Key points should be occupied by redoubts as large as Hyde Ferry Fort. Within this inclosing line should be built one or more strong redoubts to serve as citadels or keeps to the outer line, and arranged to fire into the gorges of the batteries, which, being simple stockades, would not shelter the enemy should he succeed in acquiring temporary possession. Battery Donaldson, commenced while Hood's army was approaching Nashville, is completed. For its preservation the exterior slopes have been sodded by the soldiers of the field battery stationed near.

Defenses north bank of Cumberland River.-At my request the Thirteenth U. S. Infantry, Captain La Motte commanding, commenced an octagonal redoubt about three-quarters of a mile from the railroad bridge, at bend of track, where there is usually a large collection of cars. The work would cover approaches to the bridge. The ditch was excavated, parapet raised and revetted with openings left for embrasures. Little has been done to this work since the battles. It is not necessary to complete it.

Hill 210 is situated half a mile west and beyond Fort Gillem and is higher than that redoubt. From its crest an enemy could fire at long range into the suburbs of the city and could make Cumberland Hospital and the large store-houses on the Northwestern Railroad untenable. I therefore planned a redoubt in October last to hold this hill. It was not commenced for the lack of means. When, however, Hood commenced his movement on Nashville, a large battery of two bastion fronts for fifteen guns, supported on either side by rifle-pits, was built, by the aid of employes from the quartermaster's department. The 30th of November, by my request, the commanding general directed large forces of the quartermaster and railroad departments to report to me for constructing an infantry line around the city. This line was built before the battles. It commenced at the reservoir and passed over Cemetery Hill to the railroad track, and was continued thence by General Schofield to Casino Hill. From Fort Morton it passed around the Taylor barn, and thence north in rear of the Ellison house, to Hill 210. Most of the line from Hill 210 to the Cumberland River, toucbing at Gillem, Donaldson, and Hyde Ferry Forts, was a rifle-pit. This line was supported by twenty batteries, constructed with embrasures. The entrenchment is seven miles long; no shorter line, however, would inclose the store-houses and hospitals. The high range of hills, distant about three miles from the city, was entrenched by the army occupying them while General Steedman threw up lines in front of the south suburbs of the city. Thus Nashville was doubly entrenched. The line of the hills was the best army line. It in part rested on Forts Negley, Morton, and Casino Hill, but received no support from Houston, Gillem, Donaldson, and Hyde Ferry Forts, and could not, therefore, be