40 PROCEEDINGS OF THE 



explosion that is required for merely the mechaDical arrangements under which 

 it is used. Gun-cotton in his hands has any speed of explosion, from 1 foot per 

 second to 1 foot in y^W ^^ ^ second, or to instantaneity. The instantaneous ex- 

 plosion of a large quantity of gun-cotton is made use of when it is required to 

 produce destructive effects on the surrounding material. The slow combustion ia 

 made use of when it is required to produce manageable power, as in the case of 

 gunnery. It is plain, therefore, that, if we can explode a large mass instanta- 

 neously, we get out of the gases so exploded the greatest possible power, because 

 all the gas is generated before motion commences, and this is the condition of 

 maximum effect. It is found that the condition necessary to produce instanta- 

 neous and complete explosion is the absolute perfection of closeness of the 

 chamber containing the gun-cotton. The reason of it is, that the first ignited gases 

 must penetrate the whole mass of the cotton, and this they do, and create com- 

 plete ignition throughout, only under pressure. This presure need not be great. 

 For example, a barrel of gun-cotton will produce little effect and very slow com- 

 bustion when out of the barrel, but instantaneous and powerful explosion when 

 shut up within it. On the other hand, if we desire gun-cotton to produce mechan- 

 ical work, and not destruction of materials, we must provide for its slower com- 

 bustion. It must be distributed and opened out mechanically, so as to occupy a 

 larger space, and in this state it can be made to act even more slowly than gun- 

 powder ; and the exact limit for parposes of artillery General von Lenk has 

 found by critical experiment. In general, it is found that the proportion of 

 11 lb. of gun-cotton, occupying 1 cubic foot of space, produces a greater force 

 than gunpowder, of which from 50 to 60 lb. occupies the same space, and a force 

 of the nature required for ordinary artillery. But each gun and each kind of pro- 

 jectile requires a certain density of cartridge. Practically, gun-cotton is most 

 effective in guns when used as |^ to ^ weight of powder, and occupying a spaca 

 of 1 J^ of the length of the powder cartridge. The mechanical structure of the 

 cartridge is of importance as affecting its ignition. The cartridge is formed of a 

 mechanical arrangement of spun cords, and the distribution of these, the place 

 and manner of ignition, the form and proportion of the cartridge, all affect the 

 time of complete ignition. It is by the complete mastery he has gained over all 

 these minute points that General von Lenk is enabled to give to the action of gun- 

 cotton on the projectile any law of force he pleases. Its cost of production is 

 considerably less than that of gunpowder, the price of quantities which will pro- 

 duce equal effects being compared. Gun-cotton is used for artillery in the form 

 of a gun-cotton thread or spun yarn. In this simple form it will conduct combus- 

 tion slowly in the open air, at a rate of not more than 1 foot per second. This 

 thread is woven into a texture or circular web. These webs are made of various 

 diameters, and it is out of these webs that commoo rifle cartridges are made, 

 mereiy by cutting them into the proper lengths, and. inclosing them in stiff cylin- 

 ders ot pasteboard, which form the cartridges. (In this shape its combustion in 

 the open air takes place at a speed of 10 feet per second.) In these cylindrical 

 webs it is also used to fill explosive shells, as it can be conveniently employed in 

 this shape to pass in through the neck of the shell. Gun-cotton thread is spun 

 into ropes in the usual way up to 2 inches diameter, hollow in the centre. This 

 is the form used for blasting and mining purposes ; it combines great density with 



