_Hammerless Guns._--Among improvements in shot guns the so-called “hammerless” feature is a noteworthy departure. This hides the hammers in the breech and cocks them by the act of breaking down the gun. In Fig. 282 is given a section and plan view of the Greener mechanism, which was patented July 6, 1880, No. 229,604, and was one of the first guns of this kind put on the market. The hammers A are constructed as elbow levers. Their upper ends have each a round point adapted to strike through a small hole in the breech onto the cap of the cartridge. The lower front portions of the hammers are extended forward and curved inwardly toward each other, so that their inner ends nearly meet. C is a pendent hook jointed to the barrel, and when the latter is tilted, as shown in dotted lines, the hook acting upon the forwardly projecting arms of the hammers turns them backward to the cocked position, in which they are retained by the dogs B engaging with their notches. As the hammers move back the mainspring is compressed, and when the dog B is removed from the notch by pulling on the trigger, the hammers are released and the gun fired. _The rebounding lock_, now universally applied to shot guns, is another comparatively recent improvement. This promotes safety by causing the hammers to be normally and automatically held away from the firing pins. The first practical form of this lock was patented by Hailer, July 26, 1870, No. 105,799, in which a single spring serves to deliver the blow of the hammer and also withdraws the hammer from the firing pin. A marked tendency in shot guns in late years is toward a reduction in bore, many sportsmen now using a 28 gauge in preference to the old regulation 12. Nearly 5,000 patents have been granted in the United States for firearms, and about 2,400 for projectiles. The most important of the latter is the torpedo, of which the Whitehead, or fish torpedo, which supplies its own means of propulsion, is the best known and most used. It was first brought out in 1866 by Whitehead, at Fiume, a port of Hungary. The Gathmann aerial torpedo, weighing 1,800 pounds and carrying 625 pounds of wet gun cotton, is designed to be fired from a gun 44 feet long and 18 inch bore, and is supposed to have a range of ten miles. Tests are about to be made under special appropriation of Congress, and if its claim can be substantiated, it may become the most destructive engine of warfare known.