This explosive agent, also inferior to dynamite, is used, though not very extensively, by the French for their submarine mines. _Horsley's Powder._--Horsley's powder is a chlorate mixture formed of potassium, chlorate, and galls. This explosive mixture was formerly used by Captain Harvey for his towing torpedo, but has recently been discarded for compressed gun-cotton. _Abel's Detonation Experiments._--The following are the results of experiments carried out by Professor Abel, C.B., F.R.S., on the subject of detonation:-- 1.--A fuze containing rather more than 1 ounce of gunpowder, strongly confined, exploded in contact with a mass of compressed gun-cotton, _only inflames it_, although the explosion of the fuze is apparently a sharp one. 2.--45 grains of fulminate of mercury, exploded unconfined on the surface of a piece of compressed gun-cotton, only inflames or disperses it. 3.--A fuze containing 9 grains of fulminate of mercury, strongly confined, exploded in contact with compressed gun-cotton, or dynamite, detonates it with certainty. 4.--An equal quantity of fulminate of mercury, similarly confined, does not detonate _uncompressed_ gun-cotton in which it is imbedded, but merely disperses and inflames it. 5.--150 grains of compressed gun-cotton, detonated in proximity to dynamite, _detonates the latter_. 6.--3 ounces of dynamite, and very much larger quantities, detonated in contact with compressed gun-cotton, only disperses it. 7.--A wrought-iron rail can be destroyed by detonating 8 ounces of compressed gun-cotton placed unconfined on the rail. 8.--A piece of wet gun-cotton, quite uninflammable, removed from a fire, and detonated upon a block of granite, using a small primer of dry gun-cotton, shatters the block. 9.--A submerged charge of wet gun-cotton, open on all sides to the water, and merely confined around the dry initiative, or primer, by means of a net, can be exploded. _Explosive Agents in Torpedoes._--The explosive agents that at the present time are most generally used in torpedoes are gunpowder, gun-cotton in the wet compressed state, and dynamite, and these may be compared as to their properties and their explosive effects. _Gunpowder._--Gunpowder is a familiar material, in general use for all military purposes. It can be handled and transported with safety and ease, and it can be fired by ordinary methods. But for submarine purposes it has the disadvantage of being very easily injured by water, so that it is absolutely necessary to enclose it in water-tight cases. _Gun-cotton._--Gun-cotton is free from liability to accidents, and in this matter, and the safety of its manufacture, it compares favourably with gunpowder.