velocity than the other, which exerts its action more evenly. Powder of larger grain is thus more suitable for the larger sizes of shot, and would give an increased range in usual shooting, for the shot is kept better together, and is projected to greater distances. A common way of testing the quality of gunpowder is, to rub it between the hands, and observe the darkness of the stain; the darker the stain the more inferior the gunpowder is held to be. This test is, however, decidedly fallacious, because the gunpowder may be of low specific gravity, or it may have become friable from age and other causes. Whales are shot with gunpowder proportioned to the weight of the harpoon required to kill them. Duck guns of the largest calibre are comparatively useless unless the gunpowder used is granulated according to the weight of the projectile; and the same law holds in regard to the most “mammoth” engine yet to be devised by the mind of man. Gun-cotton has been before the world for some years, but, except as a curiosity, it has attracted little public attention; neither has it gained any reputation as a projectile force. It may be prepared by steeping cotton wool for a few minutes in a mixture of nitric and sulphuric acids, thoroughly washing, and then drying at a very gentle heat. It consists chemically of the essential elements of gunpowder: viz. carbon, nitrogen, and oxygen; but, in addition, it contains another highly elastic gas, hydrogen. The carbon in the fibres of the wool presents to the action of flame a most extended surface in a small space, and the result is an explosion approaching as nearly as possible to the instantaneous: in consequence of its rapid ignition it produces a violent kick; sufficient time is not given to put heavy bodies in motion, hence it cannot be usefully employed as a projectile agent. No one who values his limbs should trifle with it, for fearful accidents have resulted from its exposure to the heat of the sun, and other very simple causes. There is an instrument used by some sportsmen, and strongly recommended by many gunmakers, for testing the strength of different kinds of gunpowder. It consists of a chamber closed by a spring, and fired like an ordinary pistol. When the powder explodes the spring is forced forward, and moves an index round a graduated circle; the more quickly the powder explodes the farther does it lift the spring; hence this is a measure of quickness of fire, but not of expellant force; and from the observations which have been made on gunpowder, it must be evident to any one who has paid the least attention to the subject, that this instrument is utterly useless. An instrument to test the comparative strength of different kinds of gunpowder is yet a desideratum in projectile science; and we cannot doubt that such an instrument will be produced, when the importance of the granulation of gunpowder is more generally known and appreciated.