[Inclosure Numbers 1.] HEADQUARTERS DISTRICT OF SOUTHERN CALIFORNIA, Los Angeles, Cal., October 22, 1861.

Lieutenant Colonel JOSEPH R. WEST,

En route to Fort Yuma:

I have received and forwarded Captain McMahon's resignation, but it was not made in form and should have been directed to the general commanding the Department of the Pacific. (See paragraph 1647, Revised Regulations of the Army.) Leave the captain in arrest at Camp Wright, if he would prefer staying there to going on with his company, until orders in his case are received from department headquarters, provided he forwards through you his resignation, as required. Otherwise let him go on to Fort Yuma. I send you the Revised Regulations. Observe Article III and Acticle XXVI. Have your officers and no-commissioned officers recite their tactics, commencing at the beginning of the first volume and going through, seriatim, both volumes. Report at the end of each month the progress you have made. It will be important that you at once send forward a party, even if they make forced marches, to clean out the wells. Perhaps Carrillo and his men and Dean can do this. To be certain that you have not too many men and animals at a watering place at one time, you had better cross the desert by companies, each one day behind the other. Send word ahead to Colonel Andrews, that he may at once detach one of his companies as fast as yours, one by one, arrive. The companies meeting you can, if you have an understanding with Colonel Andrews, so overlap their marches with yours as not to bring two companies at the same water at once. You had better go with the advance company, that you may send back words of advice to those in the rear. All this is to be done only in the vent that the waters on the desert have disappeared and the wells become filled. Should this not be so, of course your troops can keep together. I feel great anxiety that your men make the march without suffering. Better march mostly by night from Vallecito on. Great forecast and care must be exercised by yourself in this matter. Have the men drink heartily before setting out on a march and husband their canteens of water. I desire you will report to me all the details of how you managed this matter and give me your views as to the best method for troops to cross the Yuma Desert. Do this after you have become established at Yuma. Hadji Ali, the Turk who takes this letter to you, can give you much information. Make use of him as an expressman to Fort Yuma. Send him back as soon as you youself have arrived there.

Respectfully, &c.,

JAMES H. CARLETON,

Colonel First California Volunteers, Commanding.

NOTE. - Since writing the foregoing I have ordered Colonel Andrews to send a company of infantry to help clean out the wells, commencing on the east side of the desert. So let Hadji Ali, the expressman, go on without delay.

J. H. C.

[Inclosure Numbers 2.] HEADQUARTERS DISTRICT OF SOUTHERN CALIFORNIA, Los Angeles, Cal., October 22, 1861.

Lieutenant Colonel GEORGE ANDREWS,

Commanding Fort Yuma, Cal.:

COLONEL: I am informed that the wells upon the Yuma desert have become filled with sand and require cleaning out.