Fourth. In the vicinity of New York two instances of explosion are within my recollection. The one, a magazine near the navy-yard, Brooklyn, which exploded in the early part of this century, throwing pieces of the building over into the city of New York and about the city of Brooklyn, producing no injury, so far as I can now ascertain, to buildings by the explosion of the powder. The second case occurred about 1830. The steam frigate Fulton, the first vessel of this character ever built (finished and in service in 1814), was injured by the explosion of her magazine when moored on the flats at the navy-yard. The quantity of powder on board was small, and although enough to destroy much of the vessel, it did no injury to surrounding objects. The vessel had timber sides of several feet thick, floated on two hulls, with water wheels between them.

Fifth. At Du Pont's Powder Factory, near Wilmington, Del., there have been numerous explosions from time to time. The injury done beyond the immediate locality of the mill or depot has been from fragments of the building in which the powder was stored or being manufactured, and no material injury from concussion or blast of powder.

Sixth. The recent test of the 20-inch gun at Fort Hamilton, near New York, was another instance where the effect of blast of powder was observed with a charge of 125 pounds of powder. Men were stationed directly on the line of fire, distant about seventy-five feet from the muzzle and screened by the river-bank that rose about twenty feet above their heads and about twenty-eight feet below the level of the axis of the gun prolonged. They experienced no inconvenience from the blast.

Seventh. Referring to European experience, I may call your attention to the depot magazine of the French army at the siege of Sebastopol in the Mamelon Vert in 1855. It contained 15,400 pounds of powder. It occupied the center of the work, was sunk below the parade, and made bomb-proof above and around by earth and logs similar in most respects to that at Fort Lyon. It formed a crater extending to the limits of the terre-plein of this small work, but did no material injury to the rampart or even the parapets. Two batteries, distant fifty yards from the center of the magazine, were injured; 140 men were killed and wounded, some by the first effect of the explosion, others by the masses of earth, stone, and timber that were carried a considerable distance. Beams were thrown into the Russian lines.

Eighth. In 1840 the English and Turkish fleets bombarded St. Jean d'Acre, blowing up an extensive arsenal within the limits of the defenses. It was situated in the ditch, with ramparts on each side, about fifty feet from the building. The explosions formed and extensive crater extending under the two ramparts, making a breach in each of them, killing and wounding about 1,600 men, who, at the moment of the explosion, were on the rampart adjacent to the arsenal. The quantity of powder in this extensive building could not be ascertained, although it was known to fill building, with some exposed in the court-yard in the open air. The mass of stone, earth, and timber appears to have caused the death of the troops.

Ninth. We have numerous instances of the blowing up of ships of the line, as the French admiral's ship off Aboukir, and of the Turkish admiral's ship at Navarino, where destruction of the ships was entire and complete, but no effect is known or supposed to have followed from the expansion of the gases acting upon the surrounding atmosphere.

Tenth. The square tower of Brescia, of seventy feet high and eighteen feet "out to out," was destroyed in 1769 by the explosion of bun-