it is moving forward (sideways it would be in the top) as indicated by the straight arrow,—it is evident that the left half rotates with the general motion of translation of the bullet, and the right half backwards against this motion, and therefore that on the left side it is moving quicker relatively to the air through which it is passing than on the right side. And its rough surface preventing the air escaping round it on that side, while it, as it were, assists it on the other side, the air becomes denser where shown by the dark lines, and tends to deflect the bullet in the other direction, that is, in the direction in which the anterior or front surface is moving.[*]
No. 2.
Looking at the bullet sideways.
If the bullet rotate on a horizontal axis at right angles to the direction of its motion of translation (that is, like a top thrown spinning with its point sideways, when it would strike the object thrown at with its side), shown in the diagram No. 2; if the anterior portion be moving, as shown by the arrow, from above downwards, it is evident, for the same reasons, that the air will become denser, as shown, and assist the action of gravity in bringing the ball to the ground—that is, decrease the range. A spherical bullet resting on the bottom of the bore of a gun would always have a greater tendency to rotate in this manner than in a contrary direction; for the friction against the bore would be augmented by the weight of the ball in striking against the bottom, and diminished by it when striking against the top.
Shot were constructed in 1851 to try the effect of rotation in the above-mentioned and in the opposite directions. They were made excentric, that is, lop-sided, by taking out a portion of the metal on one side, and replacing it either with a heavier or lighter body. The manner in which they would rotate was, therefore, known; for, not to use too scientific language, the light side moved first, and according to the relative positions of the heavy and light side when placed against the charge so the rotation took place. Thus, when the light side was resting against the bore of the gun, the rotation was exactly contrary to the direction shown in diagram No. 2; and a range of 5,566 yards was obtained from a 10-inch gun, being 916 yards farther than with a concentric shot from the same gun. The deflections to the right and left were proportionately large, according as the light side was placed to the left or right.
We need not specify further; this will be sufficient to show the reason why the smooth bore with a spherical bullet never made a straight long
- This tendency is found in practice to overcome the tendency that there is for the
ball to be deflected in the opposite direction, from the greater friction arising from the greater density of the air pressing against the anterior surface than against the posterior surface.
