As viewed from the decks of the U. S. steamer Rhode Island at a distance of some twelve miles, the first thing observed was a bright flame, which suddenly leaped into the air a height that would subtend some 6 or 8 degrees of arc. This flame was filled with bright points or coruscations that made its appearance very beautiful. Some ten seconds after the appearance of the flame two sharp and ringing reports, about as loud as those from a 6-pounder brass gun, and following each other in rapid succession, were heard directly over the point of observation. At the same instant the vessel was sensibly jarred and shaken, and upon one of the vessels of the squadron some window glass was broken by the concussion. Immediately following this, a low, rumbling noise like distant thunder was heard in the direction of the explosion, and all was then quiet. The jar and noise of this explosion were apparent at points from 60 to 100 miles removed from it - namely, at Beaufort and New Berny, N. C. Upon an examination of the fort the next morning, no perceptible effects could be seen to have been produced upon the work. The edges and crests of the parapets and traverses remained as sharp and well-defined as ever. The grass covering their surfaces had not been stripped from them. No slides or craters in the parapet could be observed. The stockade from the north-east bastion was intact, and the wooden barracks and other buildings about the fort were still standing. The three smoke-pipes in the wrecked steamer, which was some 900 yards from the exploded vessel, were still standing. It is not believed that any guns were dismounted, and as the fort replied to the fleet for the first hour and a quarter of the fight upon the 24th instant, it is not probable the garrison were so much demoralized as to unfit them for service. The position of the fort, barracks, stockade, & c., are shown on sheet Numbers 2.* It is very much to be regretted that greater injury to this work did not result from this experiment, but it is believed a glance at the effects produced in a number of recorded cases of explosion, taking especial note of the distances beyond which no destructive action was experienced, will show that this explosion was not an exception to those that have preceded.
In April, 1585, a powder vessel, the Hope, was sent from Antwerp against the bridge erected by Alexander Farnese, prince of Parma, across the Scheldt. The vessel was about eighty tons burden, and contained 7,000 pounds of powder. The arrangement of its stowage was as follows: along the whole length of the hold was laid down a solid flooring of brick and mortar, one foot thick and five feet wide. Upon this was built a chamber of marble mason work, forty feet long, three and a half feet broad, as many high, and with side walls five feet in thickness. In this the powder was placed, and it was covered with a roof six feet in thickness, formed of blue tombstones placed edge wise. Over this crater rose a hollow cove or pyramid made of heavy marble slabs, and filled with stones, cannon balls, blocks of marble, chain shots, iron hooks, plow counters, & c. The spaces between the mine and sides of the ship were likewise filled with paving stones, ironbound stakes, harpoons, and other projectiles. The powder was exploded by means of clock-work, and at the instant of explosion the vessel was lying alongside of the bridge. The total length of the bridge was 2,400 feet and a breech but 200 feet long was made in it. It is stated that houses were toppled down miles away, and that some were killed by the concussion of the air, at a distance of 300 yards from the exploded vessel.
* To appear in the Atlas.