Numbers 30. Report of Captain D. B. Harris, C. S. Engineers.

ISLAND Numbers 10, March 9, 1862.

COLONEL: I have the honor to inform the general that there are now mounted at this point thirty-four heavy guns; twenty-four of these guns, of which nine are rifled 32s, five 8-inch columbiads, and ten smooth-bore 32s, are distributed in five different batteries on the main-land. The other ten guns, composed of the Belmont rifled gun, one 8-inch columbiad, and seven smooth-bore 32s, are in two batteries on the head of the island. These guns are protected by good parapets, are all in barbette on center pintle carriages, and, with the exception of Battery Numbers 1, are in good fighting condition; that battery, consisting of six guns, is now overflowed a few inches above the platforms, and cannot of course be of much service until the river falls. The floating battery, consisting of one rifled 32 and eight 8-inch columbiads, has been moved from the position indicated on the map which Captain Gray sent by Major Meriwether to the general to the north side of the island for the better protection of the channel of the river on that (the Missouri) side. Another battery of five guns on the island will soon be ready for use.

The banks of the river are caving in very fast, and we will be under the necessity of erecting new batteries in rear of two, if not more, of those already constructed, and we will be fortunate if we do not lose and of the guns, if what we hear is true in regard to the land-slides that sometimes occur on the Mississippi.

The banks of the river both on the main-land and island being generally as high as anywhere else makes it necessary to locate our batteries too near the river for permanence or even safety. The upper portion of the island is covered by a growth of heavy timber, which interferes with and retards the construction of our batteries there. I very much regret the general has not been able to make a personal inspection of this position and give Captain Gray and myself the benefit of his suggestions in regard to the best mode of defending it. We still indulge the hope he may yet do so.

After the necessary batteries are constructed we think it would be advisable to turn our attention to the cremaillere lines and postpone the construction of the redoubts which the general contemplated in his plan of defense on the main-land and the island till those lines are completed.

It is very important as soon as the river falls to complete the line already commenced by Captain Gray from the river to the lake. No timber has yet been cut on the Missouri side of the river; it is very heavy, and if necessary to be cut with expedition will require a large number of axmen. Captain Gray and myself do not think it advisable to spend much labor in that way at this time, there being a belt of cleared land from one-half to three-fourths of a mile in width opposite the island, which would give us a good view of the enemy should he attempt an approach in that quarter, which is impracticable, Captain Gray says, at the present high stage of the river, and not easy to accomplish at any time.

There are no very commanding positions on the island or main-land. The banks of the river on the island and this shore are, however, 10 to 15 [feet] higher than those on the opposite shore.

I spoke to General McCown several days since in regard to the construction of redoubt, as directed by the general, near New Madrid,