286 ANNUAL REPOET SMITHSONIAN INSTITUTION, 1908. 



grains are most likely to give good combustion, and that cord or tube 

 comes next ; on the other hand, a flat ribbon is likely to burn more 

 uniformly, although, again, a variation in the rate of combustion at 

 different intervals of time may just be what is wanted. 



The conviction has grown of late that in addition to being smoke- 

 less a powder should also be flameless, so as not to disclose the posi- 

 tion of an attacking force. 



The military powders suffer, in the first instance, from irregular 

 shooting. In the case of sporting powder, it is necessary to carry 

 out shooting tests with every small batch, because the reputation of 

 a firm depends on keeping powder out of the market which is in the 

 slightest degree deficient. Careful blending has to be resorted to in 

 order to obtain absolutely uniform results throughout. 



Of other difficulties in manufacture I will mention only a few. 

 The treatment of a powder under rolls is to a certain extent guided 

 by rule of thumb. It is all very well to look through the paste, the 

 sheet may appear quite transparent to a good and experienced eye, 

 yet small nodules of nitrocellulose may have escaped solution for a 

 long time. The constant crackling heard when rolling thin sheets 

 plainly points to such isolated and undissolved fibers. Incorporating 

 in a kneading machine does not improve matters. Pressing powder 

 out of a die gives very good results with small diameters, but with 

 larger diameters very much depends upon the shape of and the 

 wear on the nozzle, its position among several others or relatively to 

 the die, and on whether the outer skin will contain air bubbles or be 

 cracked. If too much solvent is taken, or the proportions of a com- 

 posite solvent are not quite suitable, the density and uniformit}^ of the 

 powder will suffer. One of the greatest difficulties lies in the proper 

 drying of powder. The smaller sizes of sticks, ribbons, tubes, etc., 

 are easier to deal with. The larger and thicker ones, hoAvever, some- 

 times require months to dry properly. With some powders this 

 defect is to a certain extent avoided by leaving some of the solvent 

 behind, but then, of course, we have on the one hand the difficulty of 

 not knowing exactly when the correct amount of solvent is present, 

 and, on the other hand, a certain amount of risk in that the powder 

 would in course of time undergo changes by gradual evaporation of 

 the solvent. 



Sporting powders are of two kinds, the so-called '* bulk " powders, 

 consisting of loose granules, coated or hardened by means of a 

 solvent, and the so-called " condensed " powders, gelatinized through- 

 out, and made in practically the same way as military flake powders." 

 The former are supposed to just fill a cartridge used in the old black- 



''The micro-photographs reproduced on plates .5 aud 6 woro Icindly prepared 

 by Mr, Henry de Mosenthal. 



