Relative strengths of explosives: Gunpowder 5; cordite 8; dynamite 9; guncotton 10; gelignite 10; gelatine dynamite 11; blasting gelatine 12. Guncotton is available in two forms, wet and dry. The dry, while being utilized in making bombs, is mostly used to explode the wet guncotton. For this purpose it is made up in one-ounce primers, which are perforated in the center for a detonator. These primers are packed in metal cylinders, each containing ten threaded on a tape. Each case contains six cylinders. In this state, although not as powerful, dry guncotton is much more dangerous to handle than wet, being susceptible to both shock and friction. Wet guncotton is that which has absorbed 30% of its weight in water, and is made up in 15-ounce slabs 6 x 3 x 1⅜ inches, and packed in tin foil and air-tight boxes containing 16 slabs each. Whether wet or dry, guncotton, like other explosives, can be exploded by one detonator, so long as the charges or slabs are in direct contact with each other. Dynamites include the following compounds: (1) dynamite; (2) gelignite; (3) gelatine dynamite; (4) blasting gelatine. All of these are now being used. Their advantages over guncotton are that, being soft and plastic, they can be used in bombs where it would be impossible to use guncotton slabs or primers on account of size and shape. Dynamite and its compounds freeze very easily (42° F.), becoming hard and brittle. In this state they are exceptionally dangerous, and they should be thawed before use, but this process should not be attempted by any one other than a competent person. Wooden implements should always be used for cutting and piercing holes for detonators in any of these explosives, and care should be taken to protect them from damp, as when wet they become highly dangerous. Dynamite explosives are usually supplied in parchment cartridges weighing two ounces, and are packed in boxes of 5 or 50 pounds. Lyddite and picric acid are both high explosives, used mostly in shells. They are easily melted and in this way the shell is filled. They are very safe and difficult to detonate. Ammonal. A new explosive which is absolutely safe to handle, not being sensitive to shock or even bullets. It does not freeze and can only be exploded by means of a detonator. It easily absorbs moisture and should be kept dry. Cordite. Is made in strands and is the explosive used in small arms ammunition. BOMBS There are three kinds of bombs: (1) _percussion_; (2) _ignition_;, and (3) _mechanical_. It is not possible to describe every bomb in use under these three headings, but the most typical are selected for description, although it does not follow that they are all in use at the present time, but will give a fairly good idea of what is required. PERCUSSION BOMBS. 1. Hand Grenade No. 1. 2. Hand Grenade No. 2, formerly known as Mexican Hand Grenade. 3. Rifle grenade No. 3, formerly known as Hale’s Rifle Grenade. [Illustration: _HAND GRENADE NO. 1._]