HAND-BOOK OF WASHINGTON. 67 In the Gun lot are arranged many pieces of Ordnance' and piles of Balls, mostly of heavy calibre for the armament of the forts. In front of th.3 old Arsenal Square a small col lection of foreign Brass Cannon will attract the notice of the visitor, who will perceive by the in scriptions that some of them are trophies of the success of our Arms at Saratoga, Yorktown, Niagara, and Vera Cruz. The Guns and Car riages of Duncan’s Field Battery, which performed distinguished service on nearly every field of battle in the Mexican War, are likewise preserved at the Arsenal, as a saluting battery. On the West side of the Arsenal Grounds, near the river, are two pyranvdal structures which often attract the curiosity of visitors and of persons passing by the Arsenal. These buildings contain an apparatus called a Ballistic Pendulum, which is used for testing the force of Gunpowder when fired in heavy Ordnance, and also for trjdng many other interesting experiments in Gunnery.