722 THE POPULAR SCIENCE MONTHLY. 



from Holland and Germany. The alders and willows in the planta- 

 tions of the factory furnish hut an insignificant supply, probably not 

 enough to make a dozen barrels in the year. They are grown for the 

 most part to form screens around and between the houses, so as to di- 

 minish the danger resulting from a possible explosion. The wood em- 

 ployed is of three kinds alder and willow, which are used for common 

 powder, and black dogwood for fine rifle-powder for the Snider and 

 Martini-Henry. The latter wood is really a kind of buckthorn (Hham- 

 nus frangula), of slow growth, and consequently close grain, which 

 forms dense thickets in the forests of Germany, and is also found in 

 the north of England and elsewhere. It is imported in bundles of 

 slender rods about six feet long, and enormous quantities of these 

 bundles may be seen stacked in the fields of the factory. There it is 

 kept for at least three years, though generally it is allowed to lie in 

 store for a much longer time. Some wood has been kept for twenty 

 years, protected from the weather by a roof of thatch, and is still per- 

 fectly sound. Strange to say, comparatively little dogwood is used in 

 the powder-factories of Germany, though it is quite certain that it 

 supplies the best charcoal for the purpose. 1 The old plan for charring 

 wood was to burn it in pits, and this is still the practice abroad, but 

 for many years the charcoal at Waltham has been manufactured by 

 sawing the wood into short lengths, and packing it into iron cylinders 

 called " slips," which are placed on a small carriage, and run into a 

 retort very like those used in gas-works. Here the slip is exposed to 

 the flames for a period varying from two and a half to three and a half 

 hours, the gas issuing from the wood in the process being utilized as 

 fuel ; and the superintendent of the work knows when the wood is 

 completely charred, by the peculiar color with which the combustion 

 of the gas tinges the fire. As soon as this appears, the slip is with- 

 drawn and cooled. The charcoal when taken out is ground in a ma- 

 chine like a colossal coffee-mill, and then, like the sulphur, sifted in a 

 slope-reel. 



The three ingredients are now ready for the regular process of 

 manufacture to be commenced. Up to a certain, point (the formation 

 of the " press-cake") the process is the same for whatever purpose the 

 gunpowder is intended, but at that point it divides into two branches, 

 according as it is to be used for heavy guns or smaller weapons. We 

 shall, therefore, first trace the various stages of the manufacture up to 

 the press-house, and then explain the method of making the various 

 kinds of gunpowder, and the objects desired to be obtained by these 

 modifications. 



1 M. Proust's experiments on charcoal, made from various woods, give the following 

 results: 12 grains of charcoal of each wood, mixed with 60 grains of saltpetre and ig- 

 nited, yielded the following proportions of gas in cubic inches : Dogwood, 80 to 84 ; 

 willow, 76 to 18 ; alder, 74 to 15 ; filbert, 12 ; fir, 16 ; elm, 62 ; oak, 61 to 63. The im- 

 portance of not overheating the wood is shown by the fact that, when the charcoal con- 

 sisted of overheated willow, the yield of gas was only from 59 to 66 cubic inches. 



