Apalachicola.--Bay entered with two fathoms through West Pass; six feet at high water across shoal situated three miles from city, crossing on a course due north directed upon city; seven and a half feet can be carried at high water across (or around) this shoal through a crooked, circuitous channel by way of Cat Point. This shoal is the bar of the river, and the six feet and seven and one-half feet channels are the only ones leading from the bay to the city and into the river. From this shoal to the junction of Chattahoochee and Flint, the head of tide-water, nine to twelve feet can be carried at all seasons. The only trouble in entering the river from the bay arises during the prevalence of northers, which reduce the depth of water on the shoal (or river bar). The east winds which always succeed soon fill up the full ordinary high-water depth, however. River passes through dense cypress swamps, is narrow, gives off small side channels and bayous, forming islands, but the channel is plain and easily found.

Chattahoochee.--Head of navigation is Columbus (a town of 18,000 inhabitants); highest water in January; has seen water at Columbus rise twenty feet in one night from heavy rains. In December, January, February, and March, six feet can be relied upon from Apalachicola City up to Columbus, and in June, July, and August (the lowest months), three to four feet, and in some seasons more than three to four feet can be had during the low months. In April and May the water is well up, deep enough for the first-class steamers of those rivers, which have stern wheels and are loaded to draw from four to six feet, and have a length varying between 100 and 170 feet. The river varies between 200 and 450 feet in width. About fifteen miles below Columbus occur the Oocha Shoals, where the channel, partially artificial, is very narrow, being cut through soft rock. There is no difficulty here, however, unless an enemy obstructs the channel, which he can easily do in consequence of its being narrow. It would be difficult for a large side-wheel boat to get through. Florence and Fort Gaines were both large shipping ports and are very healthy localities. Woodville is exceedingly healthy and the country around it, and thence to Marianna, and thence to Saint Andrew's (on Saint Andrew's Bay) is very rich, thickly settled by wealthy people. Saint Andrew's Bay affords two fathoms of water to Saint Andrew's City; thence to Marianna and Brown's Ferry the roads are excellent, and Brown's Ferry affords good facilities for depots of supplies.

Flint.--Albany is head of navigation and the river is only navigable during the rainy months (December to March inclusive), when first-class steamers go up to Albany. Mr. P. thinks the railroad from Macon to Albany has been extended to Bainbridge. Above Columbus and Albany there is no navigation in consequence of rocks and falls. Mr. P. was at Apalachicola City shortly after commencement of the war. There were about sixteen steamers engaged in trade upon the three rivers before the war. Mr. P. knows all the river pilots (who mostly live and own property in Apalachicola City, and their residences, and will furnish a list of them. I place the fullest confidence in the above statements of Mr. Pitfield, who is a very intelligent, truthful man, and whose occupations and opportunities have been such as to enable him to know and judge correctly as to these rivers.

M. D. McALESTER,

Captain of Engineers and Chief Engineer.