~Spiral grooves, by Koster, of Nuremberg in 1522.~ It is stated that Koster, of Nuremburg, in 1522, first suggested giving a spiral form to the grooves, and experience proved that much greater accuracy of shooting was the result. ~Damer of Nuremberg, 1552.~ In 1552, Damer, of Nuremburg, made some great improvements in rifles, but we are not aware of their precise nature. ~Koster of Nuremberg, 1620.~ Koster, of Nuremburg, who died 1630, by some authorities is said to have discovered that straight grooves did not fulfil the intentions of their inventor, and to have been the first who suggested spiral grooves in 1620. ~Robins first explained action of grooves.~ ~Robins structure of rifles.~ ~Modes of loading.~ The important stage next arrived at was the scientific explanation of the true value of spiral grooves. The honor of this entirely belongs to our countryman, Benjamin Robins, who in his Principles of Gunnery, gives a complete and satisfactory explanation of the action of the grooves in determining the flight of the bullet. Robins states that “the degree of spirality, the number of threads, the depth the channel are cut down to, are not regulated according to any invariable rule, but differ according to the country where the work is performed, and the caprice of the artificer. The most usual mode of charging rifles is by forcing the ball with a strong rammer and mallet. But in some parts of Germany and Switzerland, an improvement is made by cutting a piece of very thin leather or fustian in a circular shape, somewhat larger than the bore, which being greased on one side is laid upon the muzzle with its greasy part downwards, and the bullet being placed upon it, is then forced down the barrel with it. When this is practised the rifles are generally shallow, and the bullet ought not to be too large. ~Early rifles, breech-loaders.~ As both these methods of charging rifles take up a good deal of time; the rifled barrels which have been made in England, (for I remember not to have seen it in any foreign piece,) are contrived to be charged at the breech, where the piece is made larger, and the powder and bullet are put in through an opening in the side of the barrel, which, when the piece is loaded is fitted up with a screw. And perhaps somewhat of this kind, though not in the manner now practised, would be of all others the most perfect method for the construction of these sorts of barrels.” ON THE NUMBER, FORM &c., &c., &c., OF THE GROOVES. ~Number of grooves.~ ~Degree of spirality.~