ington and Georgetown by the falling of a ball. At ten minutes before mean noon every day, a large black ball is hoisted to a flag staff, standing on the top of the dome. This is to give warning for those who wish to get the exact time of day to look out. Precisely at twelve, the ball drops. Thus the whole Gity is informed of the exact time. John Q. Adams, who was a devoted friend of the Observatory, and who used to visit it fre quently in the last days of his life, has been known to walk all the way up to the Observatory from his lodgings, to see the ball fall. The Office hours at this Establishment are from 9 A. M. to 3 P. M.—within those hours, visitors will always find an officer ready to receive them and to show them every attention that politeness can bestow. THE WASHINGTON ARSENAL. The Arsenal occupies a fine position on the extreme southern point of the City, (called Green- leaf’s Point,) at the junction of the Eastern Branch with the Potomac, commanding a beau tiful and extensive view, over a broad expanse of water, towards the Cities of Washington and