LONG SHOTS. 259 



very useful for special purposes, half the charge would 

 be blown out without doing its share of work. On the 

 other hand, there are some combustibles as gun-cotton 

 and the nitrates which burn so fast that the gun 

 would be likely to burst before the shot could be ex- 

 pelled. Then, again, the shot must fit so closely that 

 there shall be no windage, and yet not so closely as to 

 resist too much the action of the exploding powder. 

 Again, there is the form of the shot to be considered. 

 A sphere is not the solid which passes most readily 

 through a resisting medium like the air ; and yft, other 

 projectiles, which are best so long as they maintain a 

 certain position, meet with a greater resistance when 

 once they begin to move unsteadily. The conoid used 

 in ordinary rifle-practice, for example, passes much 

 more freely through the air, point first, than an ordi- 

 nary spherical bullet ; but it the point did not travel 

 first, as would happen but for the rifling, or even if the 

 conoidal bullet " swayed about " on its course, it would 

 meet with more resistance than a spherical bullet. 

 Hence the question of " fast or slow rifling " has to be 

 considered. " Fast rifling " gives the greater spin, but 

 causes more resistance in the exit of the shot from 

 the barrel ; with " slow rifling," these conditions are 

 reversed. 



And then the common notion is that a cannon-ball 

 travels in the crurve called a parabola, and that artil- 

 lerists have nothing to do but to calculate all about 



