Letter from W. W. Corcoran, Esq., Chairman Joint Commission for Completion of Washington Monument, transmitting, in obedience to Law, the Annual Report of Lieut. Col. Thomas L. Casey, U. S. A., Engineer in Charge of the monument, detailing the work done toward the completion of the same during the year ending November 30, 1879, together with statement of moneys expended upon same, and two sheets of tracings, &c.