THE ROYAL ARTILLERY INSTITUTION 
85 
daring a course of twelve years J work. In Prussia, a drying chamber once 
blew up, but the accident is attributed to there being a stove with an iron 
smoke-pipe inside the room. At Hirtenberg the pipes which distribute 
heat are of earthenware, and the stoves are situated outside the drying room. 
Another case of explosion, which occurred near Vienna, happened in a 
magazine where gunpowder was stored as well as gun-cotton, and there was 
nothing to show that the latter had any share in the cause of it. 
Of complicated machinery the manufacture of gun-cotton requires none. 
A sort of wheel or cylinder turned by steam power, and used to free the 
cotton from wet, by centrifugal action, is the only machine that is used. 
Stoneware bottles and vessels constitute the main part of the apparatus, and 
plain iron instruments serve for handling the cotton when it is fresh from 
saturation in the acids. 
The cotton is obtained in the form of thread, spun to different degrees of 
texture and thickness according to its future application. Eor making 
artillery cartridges it is very loose and thick; for small-arms it is very close 
and fine; and for explosive purposes it is of an intermediate description. 
The acids must be pure and of prescribed specific gravities ; they are 
measured out in proper proportions (3 of sulphuric to 1 of nitric) and are 
mixed by being poured simultaneously into a stoneware vessel, and well 
stirred for some minutes afterwards. During the act of mixing some heat is 
produced, the temperature being raised upwards of 30°; when it is complete 
the mixture is put aside in a cool place and never used until at least twenty- 
four hours afterwards, in order that it may become quite cold. 
The cotton is made into skeins, each skein weighing from 4 to 6 oz. if the 
quality is coarse, and from 3 to 4 oz. if the yarn is fine. In order to clean 
it from seed and other impurities it is first washed in a dilute solution of 
carbonate of potassa, and it is then thoroughly washed in plain water to get 
rid of that solution. When properly purified it is dried and put away for 
use. 
About 12 hours before being required for immersion in the acid the cotton 
is hung up in a warm and well ventilated drying room, to expel the moisture 
which cotton ordinarily absorbesat the end of that time it is taken down 
and put into stoneware jars with tightly fitting lids, whilst a proper quantity 
of the mixed acid is measured into a stoneware pan with an iron lid. Part 
of this acid is transferred into another deep stoneware jar, open at the top, 
but fitted with a perforated iron ledge and surrounded by cold water, and in 
this second pan the cotton is immersed by small quantities at a time. 
Each separate quantity is stirred about in the acid for two or three minutes; 
when fully saturated it is raised on the ledge, and pressed, to make the 
superfluous acid run off; this done it is put back into a covered jar similar 
to the one from which it was taken. 
Fresh acid is transferred from the covered pan to the open one to replace 
what each quantity of cotton absorbs, and when a sufficient number of skeins 
(six of the coarse or nine of the fine) have been put into one jar they are 
pressed down and fresh acid is poured in until it completely covers them. 
The jar is then closed, put into a vessel of cold water, and allowed to remain 
in a cool building for forty-eight hours. 
The object of having the water round the immersion pan, and the jars of 
saturated cotton, is to carry off the heat evolved by the action of the acids 
