will be as brief as possible, knowing that your time must be to some extent taken up with communications from the interior. You must be aware ere this of a secret organization, ramified throughout the State, which has for its object a system of guerrilla warfare, and wholesale plundering. All this (learned through a detective whom we have had at work and through Governor Nye, of Nevada Territory), is to be ushered in by a general uprising of the secesh forces. We have had our eyes upon that branch of that organization here in our place, and have taken such precautionary measures that they have become alarmed and they are now stealing away by ones and twos to the place of rendezvous, which we learn is in the neighborhood of San Fernando Mission, Lower California, and from what we glean from detective source, we are satisfied that there they are now congregating, ostensibly to mine but really to raid, and have a good supply of arms and ammunition and provisions. We are no alarmists and we confide to you, as our commanding officer, what we believe to be true from the evidence before us. The programme is to rendezvous there, and when the time of rising comes to sound the tocsin of war on our coast, aided by the French in Mexico, the Mormons and Indians on our east, and the secesh among us, by a bold stroke take the State out of the Union and erect a Pacific republic. We learn that on the 7th of September a steamer will leave San Francisco for Lower California, and we write this to-day so that you may be able to take advantage of that steamer to send a spy there to ascertain the correctness of this statement. We have written Governor Low before of this organization; also to Governor Nye, but these matters have so impressed us here that we felt it our duty to lay them before you. There is a military company here, but at present unarmed, which company hereby, through its commanding officer, tenders its services to move at once when ordered. That a great day is coming upon the people of this coast we feel satisfied and we may as well realize it first as last; for our part we expect it and we are ready. These forces are organizing and drop off for the rendezvous in small squads, the hard times favoring this emigration movement. One Stepfield who we feel sure has a commission from Jeff. Davis, is the grand sanhedrim here, and he has a man by the name of Edwards with him in the capacity of a spy. They have gone and the men are following one at a time. We have abundant testimony here obtained from men who belonged to the organization, but drew out when they found out the real object. This testimony we do not like to commit to paper, but you can have it when you deem it necessary. We will not trust more to paper now. Should you at any time need our services either here or elsewhere, command us.

Very respectfully, your obedient servant,

D. C. MITCHELL,

Captain Alpine Rifles.

O. F. THORNTON,

Of Mount Bullion.

G. W. MAULL.

W. I. JOHNSTON,

County Treasurer.

P. S. -This was written for General McDowell, but since it was writen we learn that you are in command in San Francisco and we direct to you.

Respectfully,

D. C. MITCHELL.