66 



the curve will be in a waved form. And as it is a mere matter of chance 

 where the bias of a projectile may be in a gun, it is uncertain where the 

 shot may fly to. The spinning motion in a great measure counteracts 

 this ; and with elongated shot, as commonly made, not only might the 

 centre of gravity be out of the line of the central axis, but almost in- 

 variably, when made with its sides parallel, and with a conical point, 

 it would, when placed in the gun, have the centre of gravity behind the 

 middle of the length ; therefore, on leaving the gun, it would try to turn 

 over, to get the heavy end foremost, and it is in a great measure to coun- 

 teract this that rifling is an advantage. 



One of the chief obstacles to high angle firing (in the case of conical 

 shot), is the fact of the major axis of the cone always keeping a constant 

 angle in all the points of its trajectory. In the diagram given below, 

 it will be seen that both in the case of an angle of 35° and 15° the axis 

 (major) remains parallel to its original elevation. This is of the utmost 



importance in " target practice;" for if the angle became, say 45°, the 

 axes would become parallel to the face of the target. The impact would 

 then become oblique, and the resistance of course greater in the ratio 

 of the axis of the cone to the axes of the common round shot ; this 

 impact, in several of its properties, is but indifferently known. The 

 flame at the moment of concussion, now so generally observed, is the 

 subject of great controversy. Is it the destruction of force ? or is it the 

 carbon evolved at impact by condensation of the molecules, which, mix- 

 ing in the atmospheric oxygen, are fused by the heat generated by the 

 concussion ? It is true that the experiment of letting fall balls of iron 

 from a great height into a well has had the effect of visibly raising the 

 mercury in the thermometer ; yet this heat is incapable of combustion, 

 being at too low a temperature. Some think it to be the compression 

 of the atmosphere to such a degree as to produce solidity, and in that 

 state to evolve electrical properties. One thing remains certain, its ap- 

 pearance in almost every case where steel shot, or shell, is fired against 

 a resisting substance of iron. Would it not be possible to measure its 

 intensity by means of a thermetrical index attached to the target ? Pro- 

 fessor Tyndall, E. E,. S., has shown that heat generated by impact 

 increases as the square of the velocity, so that the heat of impact in- 

 creases in the same ratio as velocity is augmented. Now, the velocity 



