field-works are liable to frequent injury by storms. The garrison should keep them in order. Those that have been built for two or three years, of perishable material, must necessarily require repairs; gabions, fascines, boards, and nails, in contact with wet earth and exposed to the air, will decay rapidly, and in consequence parapets and embrasures crumble down and magazines leak. This large work, originally built as a refuge for the army in the event of disaster, is not needed in the present condition of the rebellion. The interior redoubts ought to be kept in order. A small garrison sufficient to hold them will control the neighborhood. At the date of my inspection Fortress Rosecrans was occupied by three artillery companies and mounted fifty-seven guns. The city was held by infantry. The depots were not within the fort. The accompanying drawing is well executed, and shows the positions and lines better than they can be described.

LAVERGNE.

Is fifteen miles and a half from Nashville. It has a redoubt which has not been garrisoned for a long period. In truth the town is desolate and requires no defenses.

BLOCK-HOUSES.

Before Hood's invasion there were seven block-houses between Nashville and Murfreesborough to protect the railroad bridges across the streams; six of these were abandoned to avoid the capture of the garrisons, and were in consequence burned by the enemy; the seventh, at Overall's Creek, stood a heavy attack until the enemy were driven away by a sortie from the garrison of Fortress Rosecrans. Between Murfreesborough and Bridgeport there are twenty-nine railroad bridges protected block-houses. These are mostly double-cased. Two large artillery block-houses defend the south bridge over the Tennessee, and ten have been erected to protect the bridges between Bridgeport and Chattanooga. Thus in the line between Nashville and Chattanooga the bridges and trestle-works, whose preservation was essential to the running of the road, have been effectually protected against guerrillas and raiding parties of cavalry by forty-seven block-houses, mostly double-cased. These block-houses always resist and drive off the infantry. Field pieces, unless in numbers, and of the caliber of 12-pounders, cannot reduce them. They have performed a most important service, and it was a very happy application of the double-cased block-house. Had they not been used it would have been necessary to have built small redoubts with single block-houses inside as keeps. The rectangular form of the block-house is defective, as the fire on the capital is a single musket. Those now in process of construction are octagonal. No new defensive works are required on this line. Drawings of Bridgeport, Stevenson, and Murfreesborough accompany this report.*

Very respectfully, your obedient servant,

Z. B. TOWER,

Inspector-General of Fortifications, Mil. Div. of the Mississippi.

MACON, GA., April 28, 1865-5 p.m.

Major-General SHERMAN:

An officer under flag of truce from Columbus reports that Canby has captured Spanish Fort and Mobile, with the garrison of the fort. Selma

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*See Plate CXII, Maps 1,2, and 3, of the Atlas.

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