The report of the Secretary of War ad interim exhibits the operations of the Army and of the several bureaus of the War Department. The aggregate strength of our military force on the 30th of September last was 56,315. The total estimate for military appropriations is $77,124,707, including a deficiency in last year's appropriation of $13,600,000. The payments at the Treasury on account of the service of the War Department from January 1 to October 29, 1867--a period of ten months--amounted to $109,807,000. The expenses of the military establishment, as well as the numbers of the Army, are now three times as great as they have ever been in time of peace, while the discretionary, power is vested in the Executive to add millions to this expenditure by an increase of the Army to the maximum strength allowed by the law. The comprehensive report of the Secretary of the Interior furnishes interesting information in reference to the important branches of the public service connected with his Department. The menacing attitude of some of the warlike bands of Indians inhabiting the district of country between the Arkansas and Platte rivers and portions of Dakota Territory required the presence of a large military force in that region. Instigated by real or imaginary grievances, the Indians occasionally committed acts of barbarous violence upon emigrants and our frontier settlements; but a general Indian war has been providentially averted. The commissioners under the act of 20th July, 1867, were invested with full power to adjust existing difficulties, negotiate treaties with the disaffected bands, and select for them reservations remote from the traveled routes between the Mississippi and the Pacific. They entered without delay upon the execution of their trust, but have not yet made any official report of their proceedings. It is of vital importance that our distant Territories should be exempt from Indian outbreaks, and that the construction of the Pacific Railroad, an object of national importance, should not be interrupted by hostile tribes. These objects, as well as the material interests and the moral and intellectual improvement of the Indians, can be most effectually secured by concentrating them upon portions of country set apart for their exclusive use and located at points remote from our highways and encroaching white settlements. Since the commencement of the second session of the Thirty-ninth Congress 510 miles of road have been constructed on the main line and branches of the Pacific Railway. The line from Omaha is rapidly approaching the eastern base of the Rocky Mountains, while the terminus of the last section of constructed road in California, accepted by the Government on the 24th day of October last, was but 11 miles distant from the summit of the Sierra Nevada. The remarkable energy evinced by the companies offers the strongest assurance that the completion of the road from Sacramento to Omaha will not be long deferred.