Dynamite, called in the United States “giant powder,” is formed by mixing nitro-glycerine with certain porous substances, and especially with certain varieties of silica or alumina, these substances absorbing the nitro-glycerine. It was invented in 1867 by the Swedish engineer Nobel, who proposed to prevent the frequent and unexpected explosions of nitro-glycerine, at the same time without sacrificing any of its power. This he effected by the use of certain silicious earths as a base for the absorption of the nitro-glycerine, the experiment resulting in the new compound which he called dynamite, its transportation and handling being no more dangerous than that of ordinary gunpowder. It is not liable to spontaneous explosion like pure nitro-glycerine, nor can it be exploded by moderate concussion; when unconfined, if set fire to, it will burn without explosion; it may be safely kept at any moderate temperature; is inexplosive when frozen, and acts effectively under water. Its effects are proportional to the quantity of nitro-glycerine held in absorption; but under circumstances where a sustained bursting pressure is required, not being as instantaneous in its action as nitro-glycerine, its effects are more powerful than those of an equal weight of the pure material. The best absorbent of nitro-glycerine for the formation of dynamite is a silicious earth found at Oberlohe, Hanover. During the siege of Paris, a scientific committee of investigation, engaged in experimenting on different substances as a substitute for this earth, selected as the best silica, alumina, and boghead cinders. Any of these, they declared, when combined with nitro-glycerine, formed a substance which possessed all the remarkable qualities attributed to the dynamite of Nobel. During the siege of Paris dynamite was used successfully by the French engineers to free a flotilla of gunboats caught in the ice on the Seine, below Charenton, by simply placing a quantity of it on the surface of the ice. The explosion dislodged the ice for a great distance, and the masses thus loosened, being directed into the current by the aid of a small steamer, floated down the stream, and left the river open. There are various other compounds of nitro-glycerine, such as dualin, glyoxiline, etc., all differing in the matter used as a base, they being generally some explosive substances; but none of them appears to have come into such general use or to be as reliable as dynamite. Many preparations of chlorate and picrate of potassium have also been used from time to time as explosive agents; but their great sensibility to friction or percussion renders them extremely dangerous; they are, therefore, not liable to come into general use. A preparation of potassium chlorate and sulphur, not liable to explode by concussion, but very sensitive to friction, is used with great effect as a charge for explosive bullets.
Dynamometer. An instrument for measuring the force of recoil in a small-arm, consisting usually of a spiral spring so arranged as to be compressed by the butt of the gun in firing. An index shows the number of pounds required to produce a similar compression. The instruments now used by the U. S. Ordnance Department are graduated to show the effect of the recoil in [foot-pounds] or units of work. This sensible change was made at the suggestion of Lieut. Henry Metcalfe of that department.
E.
Eagle. In heraldry, is used as an emblem of magnanimity and fortitude. In the Roman armies the eagle was used as a military standard, and even previous to that time the Persians under Cyrus the Younger used the same military emblem. In modern times, France, Russia, Prussia, Austria, and the United States have adopted the eagle as a national military symbol. The Austrian eagle is represented as double-headed.
Eagle, Black. A Prussian order of knighthood, founded in 1701; united with the order of the Red Eagle, or order of Sincerity, instituted by the margraves of Bayreuth.
Earl Marshal. Of England, is one of the officers of state; is the head of the college of arms, which has jurisdiction in descents and pedigrees; determines all rival claims to arms; and he grants armorial-bearings, through the medium of the kings-of-arms, to parties not possessed of hereditary arms.
Early Cannon. See [Ordnance, History of].
Earth-bag. See [Bags].
Earth-house, or Eird-house. The name generally given throughout Ireland and Scotland to the underground buildings (which in some places are called also “Picts’ houses”) which served to hide a few people and their goods in time of war. The earth-house is a single irregularly-shaped chamber, from 4 to 10 feet in width, from 20 to 60 feet in length, and from 4 to 7 feet in height, built of unhewn and uncemented stones roofed by unhewn flags, and entered from near the top by a rude doorway, so low and narrow that only one man can slide down through it at a time. Implements of various kinds have been found in them,—such as bronze swords, gold rings, etc.