line around Chattanooga, if completed as designed, will be sufficient against coup de main, and ought to stand a long siege against largely superior numbers. It is a wise precaution, however, to place in the rear of such defensive line two redoubts as citadels, which, should the first line be penetrated, would be able to drive back the assailants and restore the superiority of the defenders. There are four redoubts and a strong block-house within the main defensive line of Chattanooga, giving it an excess of strength. Three are finished and the fourth, Fort Putnam, is inclosed and could in a few days be made available. Fort Carpenter, near the river, has a good command upon the opposite bank of the Tennessee, and was doubtless designed with that view. Outside of the inclosing line of works around the city are two advanced forts of bastion from, each possessing a block-house keep. These two works cover the city so favorably as to shut out the probability of an attack upon it. If these works were improved by clearing out and deepening the ditches and by putting the guns in embrasure they could only fall by siege. Three 100-pounder rifled Parrott guns have been placed on Cameron Hill. From this high position they see over the defensive line in almost every direction. Each redoubt and fort of the Chattanooga defenses has a dry and well-constructed magazine. A large depot magazine 150 feet long and 22 1/2 fee wide has been built high up on the slope of Cameron Hill. Some further embankment is necessary to make the top bomb-proof. The site is inconvenient for the transfer of ammunition, but was selected to bring it within a large work originally contemplated to crown this hill as a citadel. This for this unnecessary and has not been commenced. To the north of the Tennessee River crowning the hill top one mile and a half distant from the south bank are five small single block-houses. They are not essentially to the defense of Chattanooga, but serve simply as strong picket positions. In fine, Chattanooga is trebly guarded, and were the rebellion still showing the same front as during the Atlanta campaign, this important depot, if moderately garrisoned, would be beyond the reach of attack.

Water-works.-In the ravine between Cameron Hill and the spur upon which Fort Carpenter stands is a large machine-shop, containing turning lathes, planing machine, a grist-mill, steam biller, and the pumps for forcing the water of the Tennessee over the ridge above, and even to the summit of Cameron Hill, if needed. These water-works, through started under the auspices of Generals Rosecrans, Morton, and W. F. Smith, have been mostly executed under Colonel Merrill's direction. The machinery was obtained from workshops and foundries in Atlanta and Chattanooga, and was fitted and sent up by mechanics from the engineer regiment. The outlay for pipes and bands has been the only expenditure made excepting that for nails, spikes, and glass necessary for the building and the construction of the water tanks, about the size of those used at railroad stations. Had Chattanooga remained as it formerly stood, a secondary base to a grand army and a vital point on the great eastern and western route, the building of these works would have proved very useful. One pipe laid from the tank on the ridge to the ordnance, quartermaster, and commissary storehouses, and thence to the railroad buildings, would be great security in case of fire, and would furnish water to the railroad, engines which now are obliged to run ore the road two miles and a half to the foot of Lookout Mountain to fill their balers. The major-general commanding the Department of the Cumberland directed labor on the waterworks to be continued, with a view to protecting the public buildings against fire. The policy of further expenditures in laying pipes is at