Corps commanders, with their officers commanding artillery and the divisions, should make themselves thoroughly familiar with the country indicated, all the roads and positions, so that no possible confusion can ensue, and that the movement, if made, be done with good order, precision, and care, without loss or any detriment to the morale of the troops. The commanders of corps are requested to communicate at once the nature of their present positions, and their ability to hold them in case of any sudden attack at any point by the enemy. This order is communicated, that a general plan, perfectly understood by all, may be had for receiving attack, if made in strong force, upon any portion of our present position. Developments may cause the commanding general to assume the offensive from his present positions. The Artillery Reserve will, in the event of the general movement indicated, move to the rear of Frizellburg, and be placed in position, or sent to corps, as circumstances may require, under the general supervision of the chief of artillery. the chief quartermaster will, in case of the general movement indicated, give directions for the orderly and proper position of the trains in rear of Westminster. All the trains will keep well to the right of the road in moving, and, in case of any accident requiring a halt, the team must be hauled out of the line, and not delay the movements. The trains ordered to Union Bridge in these events will be sent to Westminster. General HEADQUARTERS will be, in case of this movement, at Frizellburg; General Slocum as near Union Mills as the line will render best for him; General Reynolds at or near the road from Taneytown to Frizellburg. The chief of artillery will examine the line, and select positions for artillery. The cavalry will be held on the right and left flanks after the movement is completed. Previous to its completion, it will, as now directed, cover the front and exterior lines, well out. The commands must be prepared for a movement, and, in the event of the enemy attacking us on the ground indicated herein, to follow up any repulse. The chief signal officer will examine the line thoroughly, and at once, upon the commencement of this movement, extend telegraphic communication from each of the following points to general HEADQUARTERS near Frizelburg, viz, Manchester, Union Mills, Middleburg, ant the Taneytown road. All true Union people should be advised to harass and annoy the enemy in every way, to send in information, and taught how to do it; giving regiments by number of colors, number of guns, generals' names, &c. All their supplies brought to us will be paid for, and not fall into the enemy's hands. Roads and ways to move to the right or left of the general line should be studied and thoroughly understood. All movements of troops should be concealed, and our dispositions kept from the enemy. Their knowledge of these dispositions would be fatal to our success, and the greatest care must be taken to prevent such an occurrence. By command of Major- General Meade:

S. WILLIAMS,

Assistant Adjutant-General.