engaged and run past the water batteries, and opened a fire upon the rear of the town and enfiladed the ravine over the outlet of which the road from Yorktown to Williamsburg passes.

When the number of our mortars and guns are considered, the great security with which they would have been worked (owing to their careful construction and the mantelets provided for the embrasures), the positions which Batteries Nos. 1,10, 13, and 14 occupied, the co-operation of the Navy, &c., it will be admitted, I think, that the enemy's position had become untenable; that he could not have endured our fire for six hours.

It should be mentioned that Battery Numbers 1 was opened on the 1st, and with great effect on the wharf (where the enemy appeared to be receiving artillery and stores) and the town.

During the first opening of our parallels little effort was made by the enemy to interfere with our work by his fire, but after opening the parallel between the ravine and York River an incessant fire was kept up during the day with rifled projectiles, 8-inch shell, and solid shot, and 32 and 34 pounder shot, without retarding the work in the least or causing material loss of life. It is also a matter of surprise that, since our first appearance before Yorktown (April 5, and particularly since thee 15th) the ravines and woods have been filled with men, night and day, making roads, building batteries, parallels, and guarding the works, the loss of life has been most trifling. I know not the exact number, but I have reason to believe that it does not amount to a dozen. I can hardly conceive that the enemy should not have known how to use his curved fires with more effect upon those ravines. There was probably no very great supply of ammunition, and that was reserved for warmer work. His fire for the last two or three days was pretty brisk, however. During the siege operations General Woodbury, with his brigade, has been mainly engaged on the construction of roads and bridges, making gabions fascines, and constructing Battery Numbers 4 (13-inch mortar).

Captain Duane, with his command, and Lieutenants Comstock and McAlester, have superintended the siege works. All these officers have exhibited great energy, industry, and courage, and will be favorably mentioned by the commanding general, as also my aide-de-camp, Lieutenant H. L. Abbot, Topographical Engineers, who has done most valuable service in the reconnaissance and determination of the positions of the enemy and our own works.

Although it is next to impossible to fix by reconnaissance the exact trace of field works, our plans prove to be quite accurate, and the position of every one of the enemy's guns bearing on our own was marked.

Captain Stewart and Lieutenant Farquhar have been at General Sumner's headquarters engaged in examining the enemy's positions along the Warwick and in strengthening our own and in constructing Batteries Nos. 7 and 8. Had the siege continued further they would have been brought to the front. I should mention that besides the siege work mentioned extensive boyaux of communication were made down the Peninsula between the York River and Wormley's Creek, as shown on the siege plan.

I should remark that the bateaux-bridge equipage constructed during the last winter has proved of infinite service, and I believe it is the only reliable military bridge. Such equipages as the India-rubber, or even the Russian canvas-boat bridge, are of very limited applicability.

I send herewith four maps, viz: Map 1, siege plan; map 2, plan of Yorktown and Gloucester works, taken after our occupation (it must