[Sub-inclosure.]

Copy of a communication received from Lieutenant Colonel B. H. Hill, U. S. Army, acting assistant provost-marshal-general, dated Detroit, Mich., December 5, 1864.

I presume there is very little doubt that a great deal of trouble will be occasioned by the rebels in Canada this winter. It is reported to me that the number has been largely increased of late by the disbandment ion Kentucky of a rebel regiment, with directions for the officers and men to find their way to Canada.

I have the information from several sources that their numbers are so large that as soon as the ice forms in Detroit River a large force will cross the river in three parties with a view to plunder and destroy the city. I have no doubt but some such plot is now maturing. The depredations already committed from Canada by rebels harbored there have been patiently borne by the people in the expectation that the Canadian authorities would adopt measures to prevent a recurrence of them. If, however, there should be a raid on this city from Windsor there is no doubt but that the citizens will retaliate, and to avoid such a state of things I see no other way than for the Canadian authorities to station a military force along on this frontier of sufficient strength to check any outrages that the rebels may design to commit.

Signed, &c.

CIRCULAR.
HEADQUARTERS FIRST ARMY CORPS, Numbers 3.
Washington, D. C., December 17, 1864.

The following instructions will govern officers recruiting for the First Corps:

Captains will be required to secure the least forty veterans.

First lieutenants will be required to secure at least twenty-five veterans.

Second lieutenants will be required to secure at least twenty veterans.

The required number being secured, officers will not relax their efforts, but will continue their exertions to get men until ordered to join their commands.

Field officers will superintend and assist company officers in procuring men. The result of the labors of officers on this duty will have great weight in determining their claims in the final arrangement of officers.

All enlistments are to be perfected in this city, unless special orders emanating form the War Department or these headquarters are given to the contrary. In accordance with the tenor of the last paragraph of Circular 86, War Department, Adjutant- General's Office, December 1, 1864, if the Governor of a State applies for the officers appointed in this corps from such State, to de designated as recruiting officers for the corps in that State, it may enable such officers to complete the enlistments in the State. Should any such applications be made, the officers requested to be detailed will be duly notified and instructed in the matter.

Unless specially authorized as above, to enlist in the State, officers must forward their men to the Soldiers" Rest in this city. They can be assembled in small squads in any draft rendezvous, where they