When nitro-glycerine was first combined with gun-cotton in small quantities, camphor was often added, to lessen the rapidity of combustion which the nitro-glycerine was supposed to impart and also to render the compound more plastic, and to tend to prevent the decomposition of the low grade gun-cotton. But camphor being volatile, would, by its evaporation, cause the powder to constantly change in character. Castor oil has been found to be a better diluent, as this will not evaporate. As all of the smokeless powders made of a low grade gun-cotton were found to deteriorate and spoil, experiments were made with gun-cotton of the highest degree of nitration, both alone and in combination with nitro-glycerine. These experiments were first conducted in England by private parties and by the British government, when it was found that high grade gun-cotton would give excellent results if made into a colloidal solid and used alone, or in combination with certain other constituents. With a view to saving the large quantity of solvents necessary to reduce the gun-cotton, and to get a more prompt and certain ignition with a larger grain, experiments were cautiously made by the admixture of varying proportions of nitro-glycerine to the gun-cotton when dissolved, or rather along with other solvents in the process of dissolving it. It was soon found that nitro-glycerine added in quantities, even equal in weight to the gun-cotton itself, did not materially increase the rapidity of the explosion of the compound. And it was also found that high grade gun-cotton, when combined with nitro-glycerine, gave very much better results than low grade gun-cotton. I have spoken here of high and low grade gun-cotton, when in fact the word gun-cotton should be applied only to the highest nitro-compound of cellulose. The word gun cotton has always been rather loosely used. Pyroxyline would be a better word, as this applies to all grades. When cotton fiber is soaked in a large excess of a mixture of the strongest nitric and sulphuric acids, gun-cotton proper, or that of the highest grade, is produced. When weaker acids are used, lower grades of nitro-cellulose are formed. The first mentioned or highest grade gun-cotton, when thoroughly freed from its acids, has always proved to be a perfectly stable compound. The lower grades have always been found to be unstable and subject to spontaneous decomposition. Nitro-glycerine has also been erroneously thought to be a very unstable compound. But experiments have proved that, when made pure, it is perfectly stable.