powder stored within it as a magazine, containing at the time 160,000 pounds (French) of powder. Within a radius of 100 toises, 190 houses were destroyed; within a radius of 300 toises, 500 houses were greatly injured, 308 persons were killed, and 500 wounded. A stone weighing 150 pounds was thrown one Italian mile. The walls of this building were four feet nine inches (French) thick. It was two stories high, separated by a masonry arch, entirely above ground.

Eleventh. A magazine exploded during the siege of Almeida (Spain), containing 150,000 pounds (French) of powder. The Cathedral, distant 165 meters, was destroyed; 500 inhabitants were buried in the ruins of the adjacent buildings. The French trenches were filled with the ruins and large masses of stone, and pieces of the heaviest caliber were thrown in the country over the ramparts. Three-quarters of this small town, within a radius of 200 meters, was destroyed. The trenches were at the time from 600 to 800 meters distant.

Twelfth. In October, 1864, on the south bank of the Thames, between Erith and Woolwich, two powder magazines and two barges loaded with powder exploded, killing eight or nine persons and wounding others. The quantity of powder in the largest magazine (Hall's) of fifty feet square, in two floors, was 750 barrels, and in the smaller one (Lowood's) of twenty-eight by forty-eight, was 90 barrels, and in the two barges then at the wharves, 200 barrels, making the total quantity exploded about 104,000 pounds. The two magazines were 135 feet from each other, situated on the edge of the river immediately behind the dike. The two barges were moored alongside the wharves or jetties, one of which projected into the river 122 feet and the other 120 feet. Connected with these two magazines were three cottages occupied by workmen and their families; one of them, Raynor's, was seventy-one yards from Hall's magazine; another, occupied by York, was seventy yards, and the third, occupied by Silver, was fifty yards from the Lowood magazine. These two magazines and three houses, situated as above, were upon a tract of twenty acres of ground, the only buildings within a mile of the disaster. There were three distinct explosions. The first on board the barges, which tore asunder the large magazine, which latter caused the smaller one to explode. Of these magazines not a single stone remained upon another. The barges were split into fragments and hurled into the air. The embankment was destroyed, forming a crater of seventy-five feet in length and thirty feet in depth. Raynor's cottage was entirely destroyed; himself and son were killed; his wife and daughter were dug out of the ruins alive. Silver's cottage was in ruins; in it a child was killed. Silver himself was at the back door, and thrown down by the first explosion, but not hurt, while the house was destroyed by the second and third explosion. He was dug out of the ruins. No damage was done beyond the twenty acres on which the magazines and houses were built other than breaking some panes of glass and doors. The shock was felt more or less throughout London, distant at the nearest point about fifteen miles, and some statements give the distance as great as forty and fifty miles to which it was felt. A magazine a quarter of a mile from those blown up was uninjured. The store-keeper and four workmen were in this magazine at the time. The second explosion knocked them down, and a piece of iron fell through the roof. Another magazine lay at a distance of a quarter of a mile farther off, and a Government magazine one mile, to which no injury was done.

All of which is respectfully submitted.

RICHD. DELAFIELD,

General and Chief Engineer, U. S. Army.