least doubtful. The decision of this question, as well as the execution of the work if required, rests with the chief quartermaster of the department.

Pontoon shop.-This building, erected by engineer troops, is convenient for its object. The workshops of the engineer department at Chattanooga are simple in construction and economically built. In the building containing the water-works several pieces of machinery have been arranged and put in working order; but as this machinery was seized from the rebels and fitted by engineer soldiers, it has involved little outlay on the part of the Government. The timber used in engineer constructions at Chattanooga was obtained from trees cut down in the vicinity of the Tennessee River and sawed by engineer soldiers. Engineer and pioneer soldiers and soldiers of the line have done all the work on the fortifications. I omitted to state that the bridge across the Tennessee is guarded with much precaution by stockades on the piers and by a well-constructed, double-cased block-house near the north abutment. The work at Chattanooga, commenced under Generals Morton and W. F. Smith, have been mostly directed by Colonel Merrill.

DEFENSES OF LOOKOUT MOUNTAIN.

The delightful climate of Lookout Mountain caused its selection as the site of a large hospital for wounded and sick soldiers. This hospital is situated one mile and a half distant from the north point of the crest. The position is defenses by a rifle-pit across the ridge with emplacements for two batteries about half a mile south of the hospital. A small redoubt with interior block-house keep occupies the high part of the ridge toward Lookout Point. These defenses, with the forces usually in garrison on Lookout Mountain, are sufficient to protect the hospitals against raiding parties. Two little redoubts on the line of rifle-pits would have a deed vastly to the strength of the line and secured the hospital with a smaller garrison. These are not required now.

WHITESIDE.

The trestle-work across the ravine of Running Water is 780 feet long and 116 fee high in the center. Four double-cased block-houses on the slopes of the ravine see every part of this important structure, and are themselves well covered against artillery fire, unless brought so near as to expose the gunners to the murderous fire of the garrison from the loop-holes. Another block-house holds the high hill crest three-quarters of a mile distant that looks down the ravine toward the bridge. Its fire, through distant, would annoy an enemy coming from the east, which is the more natural line of approach to this position. No raiding party with field pieces could destroy this bridge thus protected. Besides, the position is but fourteen miles distant from Chattanooga on the east and Bridgeport on the west, and is difficult of access for the lack of wagon roads. All the small bridges across streams between Chattanooga and Bridgeport are protected by double-cased block-houses substantially built. These defenses have proved efficient. They have not even been attacked.

Colonel Merrill has been advised to finish the redoubts on the defensive line of Chattanooga nearly completed, with the least possible expense, and to commence no new works. The accompanying general sketch exhibits these defense with which the commanding general is already familiar. The special drawings, though not minute, given generally the forms of the redoubts and batteries and the positions of the