The range of vision of the human eye being inferior to the range of the rifle will probably be the only limit to its use; and this range will not be difficult to attain: reduction in the size of bore enables us to elongate the bullet without diminishing its weight or the accuracy of its range; but without the existence of a cavity to insure the force being applied to the head of the bullet, this cannot possibly be done; whilst all other shapes are limited in their application, and an extension of range cannot be obtained with them. Next to these two important points in the invention comes the question of expansion, whereby the grooves of the rifle are filled up with lead, and windage is as far as possible obviated. The expander I first employed consisted of a tapering piece of iron, similar in shape to the frustum of a cone, and this, when inserted into the cavity of the bullet, was flush with the bottom of the cylinder. The force generated by the ignition of the charge was exerted equally on the plug and on the leaden cylinder; the plug, however, moving more rapidly than the lead, is driven quicker into the bullet, the bullet expands, and thus the filling up of the grooves is accomplished. There can be no doubt that at the same time an upward force is exerted by the plug on the leaden bullet; and that, too, of a more elastic character than would be exerted by the gases themselves, if they were allowed to act directly with all their force upon the lead; for it is a fact beyond all dispute, that any force tending to set matter in motion gradually is more effective than that which is instantaneous in its action. Many writers condemn _in toto_ the Minié principle and its cup. Minié did not understand it; and the introduction of the cup by him was, I believe, an accident, or the best he could do by copying my mode of using it: it was not the production of his own brain. It has been urged as an argument against the use of this cup, that sometimes expansion does not occur. This, however, may easily be accounted for by the fact that the cup is not tightly fitted into the cavity of the bullet; a space is left through which the elastic fluid penetrates the cavity, the cup then has as much pressure exerted upon it behind as in front, and hence it remains undisturbed.