should be effectively performed by the troops on this line. On the departure of the Second Massachusetts Regiment Cavalry for Washington City, all the available strength of the two remaining (Sixteenth and Thirteenth New York) regiments was in compliance with instructions from your headquarters devoted to observations of the enemy's movements so far as his operations might extend to this side of the mountains. To this end it was necessary to concentrate our strength to occupy a defensible position and to relieve our camp and troops of all material which would delay a rapid movement of our whole force. All this was done, and both regiments at present occupy the hills in the vicinity of old Fort Buffalo (not quite one-half mile from our old position). But as the emergency which caused our movement is conceived to have nearly passed away it is desirable to make very soon a change of camp with the view of affording us greater facilities and accommodations. I regard it as extremely unadvisable to return to the old camp in the valley near here formerly occupied by the Second Massachusetts and Thirteenth New York Cavalry, as that location is entirely and totally unsuited for defense from either artillery or musketry, since it ison every side exposed to either a plunging or horizontal fire, and on two sides that fire could be made from forest cover which closely envelops that portion of the camp. For these reasons the reoccupation of that ground by these two regiments would, in my opinion, be objectionable, for it has not infrequently occurred heretofore that the available strength of the regiments to the extent of between 500 and 600 men has been absent at one time from the camp on scouting and guard duty. In view of these facts and of the duties to be performed here, I have to submit the following-all under the supposition that these two regiments, with perhaps a small addition of infantry or cavalry, are to remain here, viz: That three companies (one only mounted) be placed in a defensible stockade near Lewinsville between the two pikes and in a position to guard them. That three companies be placed in a defensible stockade at Annandale (one only mounted) in a position to control the Little River pike. That with the remaining force a defensible camp he chosen near this spot controlling Falls Church village, railroad, &c. Then to patrol constantly between Annandale and this point, Lewinsville and this point, on the pikes. After this disposition and in order to prevent the constant annoyance arising from small parties of guerrillas (from two to fifteen in number) passing through our lines, hovering about us, snatching up a patrol or picket here and there by ambuscade, &c., I propose to use the dismounted men at Lewinsville, Annandale (as above stationed), and at this point to establish from the Potomac to the Braddock road, on all the roads and paths leading toward our lines, a secret picket-line of from two to five miles out in ambuscade, sending the men in parties of from six to twelve, with two days' rations posting them in the night and concealing them, always changing their positions each time of posting, and with orders to interfere with no persons but guerrillas; 100 men so picketed would establish such a line and while the mounted company at Lewinsville and Annandale respectively controlled the travel, passes, &c., there, the dismounted companies at those places could furnish their quota of this secret picket or ambuscade line, the remainder being furnished from here, the central point. Concerning the system of scouting in the enemy's country, so long as the force operated against is composed of guerrillas, as Mosby's men are, men who scatter to their