CHAMBER, in military affairs. 1. Powder-chamber, or bomb-chamber; a place sunk under ground for holding the powder, or bombs, where they may be out of danger, and secured from the rain. 2. Chamber of a mine; the place, most commonly of a cubical form, where the powder is confined. 3. Chamber of a mortar; that part of the chafe, much narrower than the rest of the cylinder, where the powder lies. It is of different forms; sometimes like a reversed cone; sometimes globular, with a neck for its communication with the cylinder, whence it is called a bottled chamber; but most commonly cylindrical, that being the form which is found by experience to carry the ball to the greatest distance.