The Mississippi flows in a broad, low valley or bottom. Bluff or high grounds touch the river at but very few points of its course. The land of this bottom is of alluvial formation. The banks of the river are, as a general rue, higher than the country on either side of it. The headlands of islands are higher than their lower extremities. The up-river sides of points are higher than the down-river sides.

The height of trees of full growth on the banks of the river and on islands is everywhere about the same, say 140 feet.

To extend a line along any portion of the river, all that will be needed will be signal towers erected at chosen elevations upon the banks at an average air-line distance of nine miles apart. To extend a line from Memphis to Cairo twenty of these signal towers would be required, which it is computed would cost $30,000.

In the establishment of a line of stations from Memphis to Cairo, part of that line would be exposed to the enemy. Each station thus exposed should be garrisoned by at least two companies. This garrison ought to be protected by such earth-works and defenses as the men could construct, and should have several light guns or howitzers. Stations should also be placed, when possible, at all the principal crossing of the river likely to be used by the enemy; where main roads come into the river, by which the enemy; where main roads come into the river, by which the enemy may approach its banks, and, generally, on such points of the river banks that the garrison posted for the protection of the station may afford protection to the inhabitants of the vicinity and secure the safety of commerce. For telegraphic communication on so long a line, each tower ought to be furnished with a simple semaphoric apparatus, or machine, for aerial telegraphy, which, it is thought, would secure greater accuracy in telegraphing at great distances.

The establishment of such a line, it is supposed, would insure the holding of the Mississippi River to whatever extent the signal lines were posted.

The fact of the garrisons being known to communicate with each other would deter the assault of the enemy. No temporary attack on the intrenched posts would be likely to be successful, and no prolonged attack could be undertaken on a post which could call thus readily on others, without encountering concentrated land and naval forces.

Troops stationed in this way would become acquainted with the people of the country, and their hunting parties and scouts would become familiar with the paths and roads. Small settlements, too, would gather around these posts, and it would soon become difficult for any considerable parties of the enemy to even approach the river without detection. It would be dangerous for small parties to do so. Should. There be need of escorts for particular purposes small parties could be furnished from post to post, or gun-boat convoy could be telegraphed. This plan adopted, the settlements would realize and appreciate the protection thus extended, the banks would be in our power, and the river could then be announced as safely open to commerce. (Appendix C, Papers C, A, B1, C1, D1.)*

SIGNAL CAMP OF INSTRUCTION.

This camp has, in addition to being a school of instruction for officers and men, been a depot for the recruits of the corps.

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*Myer's report, dated December 26, 1863, with inclosures, is omitted, it being substantially quoted herein.

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