HEADQUARTERS DEPARTMENT OF THE MISSOURI,
Saint Louis, Mo., December 13, 1861.

Brigadier General LORENZO THOMAS,

Adjutant-General of the Army, Washington, D. C.:

GENERAL: On examination of the organization of the troops in this department I find numerous irregular and fragmentary bodies actually in service, but not in the manner authorized by law. It is very difficult to dispose of these in such a way as not to injure the public service or do injustice to the officers and men and the same time conform to the law and regulations.

In the case of the Fremont Body Guard, I used my best endeavors to induce them to remain in service, but they unanimously protested against it, on the ground that they were not enlisted to serve the United States, but to serve Major-General Fremont, and that on his removal their term of service ceased. I directed the captains of companies to present me their original muster rolls, which they did, and I found that they had only obligated themselves to serve as General Fremont's body guard. They said, moreover, that the mustering officer, Captain John D. O' Connell, Fourteenth Infantry, announced to them at the time of the mustering in that if General Fremont should die or be otherwise removed from the command their term of service would cease. I therefore, at their own solication and the request of Major-General Fremont, mustered them out.

There seems to have been some misapprehension at Washington in respect to the Reserve Corps and Home Guards. The former, at least the regiment stationed in this city, are regularly mustered into service for three years, without and limitation as to their place of service. They are regularly-organized Missouri Volunteers, and entitled to pay and allwances the same as any other volunteers. They will be paid accordingly. The Home Guards are not a regular organization; some have been mustered in with the reservation of serving only in this State, while others, altough long in service, have never been mustered at all. I have offered them the option to be mustered in according to law, so as to cover their past services, or to be mustered out, and receive pay only for active service in Missour away from their homes, in accordance with your instructions of the 2nd instant. Most of them will probably prefer the latter alternative. If they do, it will be very difficult to ascertain the length of their services away from home.

The engineer organization in this department is a very peculiar one and the greater part of it without any authority of law. As near as can be ascertained this organization is as follows:

Officers. Enlisted men.

Colonel Bissell's Engineer 36 925

regiment...

Two companies of telegraph 6 200

men....

One company of telegraph 3 25

guards...

Signal company.... 4 51

Force of sappers and ..... 42

miners...

Company of pioners, sappers 3 98

and miners...

Company of pontoniers... 3 100

Engineer detachment at 3 17

Ironton...

Engineer Corps, &c... 43 .....

Colonel Bissell's regiment is regularly mustered into service receiving infantry pay, with allowance for extra service, as provided by law.