136 MILITARY SCIENCES. 



endless band. For the roller B there is an endless band, G, which is 

 stretched by the roller C. The powder mass, still in its half-moist state, is 

 shaken through the hopper H, and pressed between the rollers B and E into 

 cakes, which fall by fragments into the receiver K. These powder cakes 

 are then grained. The graining-sieve {jig. 9) consists of as many sieves, 

 set one within the other, with exactly pierced parchment floors, as there are 

 kinds of powder to be produced. Here, B, C, and D are the sieves. The 

 mass is placed in D, loaded with a leaden disk, E, and by the motion of the 

 sieve the powder is formed according to the size of the holes. The dust 

 falls through the finest sieve into the chest A, and is then worked anew. 

 The very sharp-grained powders are good for military purposes, but for 

 hunting the powder is glazed in the glazing-casks. These casks {Jig. 10 C) 

 are set one behind the other on a shaft in the frame F, and made to revolve, 

 at first slowly then more rapidly, by the driving wheels A and B ; inside 

 they have laths, against which the grains strike and thus smoothe each other. 

 If the powder is to be polished at the same time, lead balls are mingled 

 with the mass. A particular process for making powder with perfectly 

 round grains is that of Champy {fig. 8). Here the mass is brought dry to 

 the barrel A, whose shaft, a, turns in the frame g ; by the pipe d a jet of 

 water is thrown upon the mass, through a very finely pierced rose ; the 

 grains form themselves, and by motion become, avalanche-like, perfectly 

 spherical. The cock c shuts off the water, and the trap e gives access to 

 the barrel. The powder, when finished, is dried in heated drying-rooms, 

 and then proved. For proving, the vertical eprouvette is very commonly 

 used {pi. 4:0, fig. 11) ; the proof-charge is placed in the small mortar a, and 

 upon it the foot of the notched staff h, which is loaded at the top, d, and 

 passes through the cross-piece,/, of the frame, e e. If the charge is now fired 

 the staflf h is driven up and retained at the greatest height it reaches by 

 pawls on the cross-piece, which catch in the notches ; the strength of the 

 powder is judged by the relative height to which the staflf is driven, a nor- 

 mal powder being taken as the standard. Another proof is that with the 

 eprouvette mortar {fig. 12), from which three discharges are made with the 

 standard powder, three with the powder to be proved, and the strength 

 determined by the average effect of these discharges. The proved powder 

 is placed, in barrels containing one cwt. each, in the powder magazine. 

 The field magazines {fig. 13, ground plan, fig. 14, longitudinal section along 

 A' B',fig. 15, cross section along C D') in batteries, &c., are partly sunk in 

 the earth at F ; a sloping passage, G, leads down to this, and a small ditch, H, 

 serves to collect all the moisture, with a view to which the floor of the 

 magazine slightly slopes towards it. The magazine is closed in, all around, 

 with filled gabions, E E ; on the top of which is a layer of fascines, D ; then 

 comes a row of air-holes, C ; and a plank cover, above which is another row 

 of fascines, and then a layer of earth, A. The door is always turned away 

 from the enemy. The permanent magazines {fig. 16, ground plan,^o^. 17, 

 cross section,/^. 18, ground plan on a larger scale, /^. 19, longitudinal sec- 

 tion on the same) are massive bomb-proof structures, G, surrounded with 

 rampart and ditch. G is the building, F the space with the rampart, A the 

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