ADJUTANT- GENERAL'S OFFICE,

Washington, D. C., February 7, 1861.

Bvt. Brigadier General ALBERT S. JOHNSTON, U. S . Army,

Commanding Deaprtment of the Pacific, San Francisco, Cal:

GENERAL: Herewith I have the honor to transmit a copy of a project fort he continuation of the work on the work on the Fort Benton and Walla Walla military road, submitted to the Secrretary of War by Captain Andrew A. Humphreys, Corps of Topographical Engineers. The Secretary approves of the same, and directs that you give the necessary instructions for carrying out its provisions. A detail of an assistant surgeon to accompany the expedition will be made from your command, whom you will instrct to attnd the citizens employed by lieutenant Mullan.

I am, general, very respectfully, your obedient servant,

S. COOPER,

Adjutant-General.

[Inclosure.] WAR DEPARTMENT, OFFICE OF EXPLORATION AND SURVEYS, Washington, January 24, 1861.

Honorable J. HOLT,

Secretary of War:

SIR: In the latter part of December I submitted to the Deaprtment, with a recommendation, the project of lieutenatn Mullan, U. S . Army, in charge of the military road from Fort Benton to Fort Walla Walla, for continuing the operations during the ensuing season through the next winter and the following spring and summer (kn all about fifteen months from 1st April next), together with an estimate of the expense of executing the work. Them amount available for this operation, including the probable amount of sales of animals and other property at the conclusion of the field- work, was estimated by Lieutenant Mullan to be on 1st April next $85,000. This sum was prbably in excess about $2. 500. Having undrstood that the above mentioned paper has been mislaid, and that it is desired I should submit a substitite for it, I beg lkeave to say that it is not in my power to state the exact number of assistants and employes and extent of soutfit and the montly cost of maintaining the party proposed by Lieutenant Mullan, nor should I wish to make out a project in detail togovern that officer, as it might cramp him and impair the efficeincy of his party. After a careful examination of his project I propose that the number of his assitnats should be one less than he asked for, and that instead of employing a physician an assistant surgeon should be detailed to accompany his escort (100 strong), and be directed byt the Surgeon- General to attend the civil employes of the party. Much of the work to be done upon the road consists in building bridges, and Lieutenant Mullan proposed that the party should winter on the route, and be employed during that season upon tose constructins, and resuming th other labors upon it in th espring, reach Fort Benotn in time to dwscend the Missouri in the latter part of the summer. Whether more time would be lost by this plan of operations, or by returning to Walla Walla toward the end of the fall and discharging the party and reorganizing it again and taking the field in the following speing, it is difficult to deciede. I propose, therefore, that discretionary authority should be given to Lieutenant Mullan to send back to Walla Walla and discharge a portion or the