At the British Association meetings of 1862, a committee of chemists and physicists was appointed to inquire and report on the so-called Austrian gun cotton. The report was published in the last meeting by Dr. Gladstone and Mr. J. Scott Russell; and we think it will be interesting to our readers to be acquainted with the principal parts of this paper. *

* We are mainly indebted for the following pages to an abstract of this report, given in the "Annual of Scientific Discovery," 1864, p. 47, and to an able and interesting ar-ticle on gun cotton in the "United States Service Magazine," April, 1864, p. 345.

Chemical Report

Since the discovery of gun cotton by Schon-bein its application to war purposes has been frequently thought of, and many experiments, with a view of using it, have been made, especially by tbe French. Such serious difficulties have, however, presented themselves that the idea gradually came to bo abandoned everywhere but in Austria. Here experimenting was kept up, and it having been reported on good authority that the experimenters had succeeded in overcoming many of the difficulties encountered elsewhere, the committee of the association applied to the Austrian Govern-ment for information, which was furnished to them. The following is a summary of the more important facts elicited. In the first place, the gun cotton prepared by Baron Von Lenk, the inventor of the Austrian system, differs from the gun cotton generally made in its complete conversion into a uniform chemical compound. It is well known to chemists that, if cotton is treated with mixtures of strong nitric and sulphuric acids, compounds may be obtained varying considerably in composition. Though they all contain the elements of nitrio acid, and are all explosive.

There is one part of the process not yet alluded to, and the value of which is more open to doubt. The treatment of the gun cotton with a solution of silicate of potash, commonly called water-glass. Some Austrian chemists think lightly of it; but Von Lenk considers that the amount of silica set free on the cotton by the carbonic acid of the atmosphere is really of service in retarding the combustion. He adds that some of the gun cotton, made at the imperial factory, has not been silicated at all, and some imperfectly; but when the process has been thoroughly performed, he finds that the gun cotton has increased permanently about three per cent in weight.

It seems a disadvantage of this material as compared with gunpowder that it explodes at a temperature of 277°; but, against the greater liability to accidents from this cause may be set the almost impossibility of explosion daring the process of manufacture, since the gun cotton is always immersed in liquid, except in the final drying.* Again, if it should be considered advisable at any time, it may bo stored in water, and only dried in small quantities as required for use. The fact that gun cotton is not injured by dampness like gunpowder, is indeed one of the recommendations, while a still more important chemical advantage, which it possesses, arises from its being perfectly resolved into gases on explosion, so that there is no smoke to obscure the sight of the soldier who is firing, or to point out his position to the enemy, and no residuum left in the gun to be got rid of before another charge can be introduced.

* In ten years' experience it is proved that this temperature is sufficiently high to insure safety of manipulation: 277° is an artificial temperature; and artificial temperatures, accidentally produced, are generally high enough to ignite gunpowder. The greater liability to accident from this cause can, therefore, scarcely be admitted.