The whole corps must be in position and report of the position must be at these headquarters by Wednesday evening next.

General Reynolds will send his mounted brigade, under special instructions to be issued from these headquarters, to make a demonstration on Chattanooga and Harrison's Landing.. A mounted force from the Fourteenth Corps will be left at Tracy City sufficient to protect the telegraph operator and act as couriers. The movement must begin to-morrow morning.

II. The movements of the Twenty-first Army Corps will be as follows: Wood's division, by the most expeditious and practicable route to Therman, in the Sequatchie Valley, with ten days' rations and eight days' short forage. Palmer's division, by the best route to Dunlap, believed to be through Irving College. Van Cleve will move with two brigades of his division and Minty's cavalry brigade; he will move the main body of the cavalry via Sparta, clearing out the rebels from Caney, and encamping the first night at or near Sparta, moving the next day on Pikeville. Two battalions of cavalry will accompany the infantry column, which will move, via Spencer, on Pikeville, and reaching there by Tuesday. Thus the whole corps and cavalry, save a brigade of Van Cleve's division and a battalion of cavalry, will be in the Sequatchie Valley by Wednesday night, and open communication between divisions, and from the corps to these headquarters via McMinncille on the left and Tracy City on the right. Van Cleve will leave a battalion of cavalry at or near Sparta to watch the flank of his route, and give warning of rebel guerrilla or cavalry movements in that direction. On arriving at Pikeville, he will without delay push a strong cavalry reconnaissance, if possible, to the Tennessee River, via Morganton, and Smith's Cross-Roads, to Blythe's Ferry and Washington, and get forward forward their reports without delay.

General Palmer will on Thursday push a brigade of infantry to Soddy Post-Office, and send advances to Poe's Tavern, and on the direct road to Harrison's, supporting Colonel Wilder's reconnaissance, which will endeavor to reach the river on that day, opposite Chattanooga and Harrison's Landing. This brigade may have the show of the head of the column, by following it with a part of another brigade and a battery to some intermediate point.

General Wood will also send an infantry brigade, to make a reconnaissance as far as the eastern edge of Walden's Ridge, by the road through Therman, showing the head of his column opposite Chattanooga.

These reconnaissances will be conducted with a show of modest concealment, indicating strength. The results must be sent to headquarters with the utmost dispatch; arrangements to insure this end must be made in advance. Should any threatening force of the rebel infantry appear, the reconnoitering parties will hold themselves in observation on the front, and report for orders. I they show nothing this side, but a strong force on the east side of the river, they will post an advance guard within observing distance, and take a good position near the valley, where all the trains will be left until further orders. Should perfectly satisfactory evidence be found that the enemy has evacuated the country and gone south, these advances should go to the river and guard it, while looking for all available means of crossing and report back information and for orders.