those points where the access up the sides of the mountain may be convenient to an enemy. The portion of the heights to be occupied by us should extend about one and three-fourths miles from the southern extremity of the ridge, with the object of protecting our supplies of water from the base of the mountain at the oft of the eastern slope and distant about one and one-quarter miles from the southern extremity of the ridge. Our principal defense should be felling tress, &c., on the sides and slopes of the mountain and on the summit wherever and approach would be practicable. We should also occupy below the base of the slope, where our supplies of water are to be drawn. The mountain affords capabilities for a strong defense, but from the extent of ground to be occupied, the condition of the roads, and the necessity o hauling water and stores up the mountain, much inconvenience may be experienced, and a certain amount of time also will be expended in completing the defenses.
The ascent of the eastern slope is through Solomon's Gap, by a road larger and steeper than by the corresponding road from the western side, and also by a road constructed by the enemy and leading up from Sandy Hook. The latter road is not too steep, but is very rough, having large stones five or six feet long in many places directly in the road. The same is true in a measure of all other roads upon the mountain. The rocks are said by those who have made roads on the mountain to be generally detached, and not to form a part of a ledge.
It is impossible to state what amount of force could be detailed from the Army at this period, with the necessity also of watching closely the enemy, to construct the necessary defenses. My estimate is that two thousand men are necessary to occupy the mountain and the eastern slope, and it would require two thousand men to work about ten days in order to put everything in condition to make a vigorous defense.
The extent and rugged nature of the ground examined and the close growth of timber and brush rendered it impossible to take measures, and the distances are accordingly taken from maps, guides, and from personal observation, without the use of instruments.
I have the honor to be, your obedient servant,
Captain, U. S. Engineers, Chief of Engineer Staff.
HEADQUARTERS FIFTH BRIGADE (NEGLEY'S), June 29, 1861-11.30 a. m.
Major F. J. PORTER,
A. A. G., Hdqrs. Dept. of Pennsylvania, Hagerstown, Md.:
MY DEAR MAJOR: From all the information as yet received the enemy has recrossed the river at Harper's Ferry on flats and boats and occupied the Maryland Heights with two regiments-said to be the Kentucky and Mississippi-numbering together about two thousand men.
First. The express arrived at General Cadwalader's at 3 a. m. from this camp. I considered it best at the time for me to come over here, and accordingly here I am.
Second. Is this movement made to mask Johnston's retreat?
Third. Is it to secure his flank while he marches against Stone?
Fourth. Has he been re-enforced, as has been asserted, and is this the first offensive movement on his part? He is likewise said to have a number of rifled cannon, a deserter asserting that the balls are not round, but flat at one end and egg-shaped at the other.