CAVALRY RAID FROM PENSACOLA.

The communications between Alabama and Mississippi are by there routes: a new one from Montgomery west by rail, from Montgomery by water to Selma, and thence by rail, and by rail from Montgomery to Tensas, and thence by water to Mobile.

The first was one finished, and a train passed over it. Soon after, the Alabama rose and washed away miles of the track. Running through a very low and swampy country, it was found impossible to keep the road in running order, and it was abandoned.

The route by Selma is scarcely ever used, as there are but few boats on the Alabama River and every rolling-stock on the railroad from Selma. Moreover, this road runs through very marshy country, and, being carelessly built, the bridges and trestles are continually being washed away.

The main transportation route is by rail from Montgomery, through Pollard to Tensas Station or Tensas River, thence by boat 26 miles to Mobile. Pollard is the junction of the Montgomery and Pensacola Railroad with the Mobile and Great Northern Railroad. The actual junction is 1 mile below Pollard. The track from Pollard to Pensacola is torn up. Between Pollard and Tensas are many bridges and long trestles. Tensas Station is built on piles, and thence to the first firm land is 3 miles of trestle-work. The destructions of this would be almost irreparable in the present state of the rebels.

From Pollard to Tensas is 60 miles, and from Pollard to pensacola is the same distance. There are many bridges near Tensas and about midway between Tensas and Pollard, the road having to cross many small, bayous, and marshes. The largest bridge is 32 miles from Tensas. It is one-half mile long, and is approached by trestle-work on both sides, so that the entire length of bridge and trestle is 1 1/4 miles. The road is protected by one regiment of infantry (Seventy-ninth Alabama) and three companies of cavalry. The latter are conscripts, and of very little use. These men have the entire 60 miles to guard. There are no block-houses or earthworks along the line anywhere. The proper place to strike first would be at Tensas Station, as that would prevent troops from mobile from coming up.

It would be well, however, to strike near Pollard at the same time, and have the two detachments meet in the center of the road, after destroying its entire length, and returned together to Pensacola. The enemy having so little cavalry in the vicinity would be unable tom interfere. Four good companies of cavalry could destroy the road, but a regiment would be better. Such a command, secretly embarked at New Orleans, as of for Texas or other out of the way place, could suddenly land at Pensacola and destroy the road before the rebels could suspect their presence. The road from Pensacola to the Tensas River is through open piney woods; is sandy and well watered. There is a deficiency of forage, though plenty of coarse grass for cattle. The latter are plentiful in that region. The importance of destroying this route may be judged from the fact that Bragg's whole army passe over it when moving up into Tennessee and Kentucky. From the time a cavalry regiment left New Orleans until its return to the same place, after destroying this railroad, need be over two weeks.

Respectfully submitted.

WM. E. MERRILL,

Captain of Engineers.