The main object of Captain Delvigne in hollowing the base was, to throw the centre of gravity forward; but a Captain Blois, in France, had previously tried this important suggestion. Captain Delvigne states, if the hollow is too deep, the expansion is too great, and the consequent friction enormous; or the gas may pass through the bullet, and leave a hollow cylinder of lead within the barrel. Sometimes the gas will traverse the sides of the bullet, and consequently the projectile is deprived of a proportionate amount of velocity; if too small, the expansion does not take place. ~Capt. Minié iron cup.~ Captain Minié, an instructor of the School at Vincennes, merely fitted into this hollow an iron cup, hoping to prevent the gas forcing its way through the bullet, and that the iron pressing upon the lead should increase the expansion. (Plate 20, fig. 7). ~Groove suppressed.~ A perfect bullet was now supposed to have been discovered, of a cylindro-ogival form, (no part was a true cylinder), having a groove originally intended to fasten on a greased patch, and in some cases the cartridge, but the patch being dispensed with, and the cartridge reversed, the groove, supposed to be useless, was suppressed. ~Results.~ People were then surprised to find that firing lost much of its accuracy, and the groove was replaced; when it was observed that any variation in its shape and in its position, materially affected the practice. Not only variations in the grooves caused great alteration in the accuracy of fire, but any modification bearing on the trunk in rear, or on the fore-ogive, altered the conditions of the firing, so that the groove became lost in the midst of so many other principles, the functions of which were so much unknown. These theoretical considerations served, however, as a point of departure for further investigations. ~Tamisier lengthened bullets.~ Captain Tamisier had not ceased for several years, concentrating his attention on the subject. He varied the length of the cylindrical part and the angle of the cone, and tried experiments with bullets of 5-in. in length, and obtained considerable range, and great accuracy with them; the recoil however was excessive, and to use such bullets heavier arms, a smaller bore, and other modifications would be necessary. ~Centre of gravity formed by blunting tips.~ He endeavoured to carry the centre of gravity to the furthest possible point forward, (which Robins suggested 100 years before), but to effect this he was compelled to flatten the fore end of the bullet, which had the disadvantage of increasing the resistance of the air to the movement of projection. ~Path rectified by resistance in rear.~ ~Many cannelures.~