230 Professor Victor Horsley [April 6, 



the apparent paradoxes presented to us are to be explained by the 

 fact that the results are wholly dependent upon the simple question 

 of the relative viscosities of the substances entered. To solve this 

 I employed the same falling bodies, and examined their entanglement 

 of air in water and glycerine respectively, and found that whereas, in 

 the case of water, Laroque's non-floating rod drove air in front of it 

 as well as probably at the side, yet when the same rod was caused to 

 fall into glycerine of high concentration there was no air in front, but 

 air-bubbles could be seen clinging to the sides of the rod. Further, 

 in glycerine the entanglement of air in the funnel formed by the base 

 of the bullet, as described by Magnus, was very striking. It 

 appeared to me that whatever air was driven in front of it was wholly 

 reflected by the sufficiently viscous fluid, and hence it must be, 

 a fortiori, still more completely reflected from the surfaces of hard 

 and soft solids like the skull and brain respectively. 



To sum up, the so-called projectile air can have no real bursting 

 effect, since, as I have demonstrated, in the first place it exerts very 

 feeble pressure, as tested on a delicate vane, and in the second place 

 it is certainly easily reflected from surfaces of but moderate density. 



The Influence of Rotation 'produced by Rifling. — It is commonly 

 thought that the spin of the bullet communicated to it by the rifling 

 of the barrel, and which is very great, causes a considerable amount 

 of the disturbance created in the interior of moist substances, which 

 is usually spoken of as the bursting or explosive effect. Kocher 

 thought that this would not be appreciable, and that the rotatory 

 movement would only cause the displaced particles to take a course 

 tangential to the surface of the bullet rather than perpendicular. 

 Although the smooth surface of the bullet of course adds force to the 

 idea that its rotation is not very effective, it is obviously a matter of 

 both interest and importance that the matter should be more closely 

 studied. Colonel Henracl made plaster casts of the tracks of shots, 

 and obtained distinct spiral markings indicative of the rotation in 

 question. Acting on this suggestion, it was easy to institute a series 

 of experiments of the following kind. Pure modelling clay of firm 

 consistence (for the influence of the water present vide infra) was 

 rendered homogeneous by kneading, shaped into square blocks of 

 varying length, and supported in a hard flat surface or in a box, the 

 ends being open. The cavity made by the bullet in entering and 

 traversing the mass was then filled with liquid plaster-of-paris, and 

 a cast obtained. Examples of such ca^-ts are before you, and they 

 completely display the rotation in question. 



The first point which has to be borne in mind is the relation of 

 the rotation to the projection or forward movement of the bullet. In 

 passing through a body of little resistance like the air, it is clear 

 that for every given unit of distance travelled, the displacement 

 evoked by the rotation must be something very small, because although 

 the bullet turns one and a half times in traversing the barrel, that 

 is nearly a yard in length, consequently, so far as the rotation is 



