480 



Intelligence and Miscellaneous Articles. 



The smallness of the deviation due to the earth's rotation, as 

 compared with the total deflection, shows that this is practically- 

 negligible. 



whitwoeth's gun. 





Projectile of 2-75 Ml. 



<p, angle of firing .... 



il 



5° 



1800 m 



6 s -8 



l'»-30 



m -63 



1 



2-2 



11° 

 2800 m 



13 s -6 

 3 m -14 



2 m -22 

 1 

 1-5 



15° 

 4200 m 

 17 s 5 



8 m. 4 



3 m -76 

 1 



2-0 



20° 



6300 m 



22 s -5 



14 m -30 



6 m -35 



1 



2*2 



30° 

 7200 m 



33 s -0 

 22 m -30 



10 m -50 

 1 

 1-8 



35° 



9000 m 

 37 s 6 

 28 m -30 



15 m -35 



1 



1-8 





~D, total deflection . . . 

 A, deviation due to the earth' 

 rotation 



Batio — 



Thus the effect of the earth's rotation contributes half the total 

 deflection of the projectile ; hence this influence cannot be neg- 

 lected. 



This deviating effect of the terrestrial rotation may give applica- 

 tions useful in ballistics. 



Thus: 



(1) When in our hemisphere the effect of the earth's rotation 

 amounts to half the deviation of a projectile to the right of the plane 

 of firing, if the direction of the rifling of the cannon be changed, the 

 deviating action of the air changes also ; the effects of rotation 

 and of the resistance of the air destroy each other ; so that the pro- 

 jectile will fall in the actual direction of the line of firing, and the 

 deflection will be almost zero. 



(2) On passing from one hemisphere to the other, the direction 

 of the rotation changes, and consequently that of the deviating ac- 

 tion on the projectile. 



It follows that — 



If the projectile does not deviate in our hemisphere owing to the 

 equal and contrary effects of the resistance of the air and of the 

 earth's rotation, these effects will be added to one another in the 

 other hemisphere, and the projectile will deviate to the left. 



If the deflection to the right in our hemisphere were double that 

 due to the rotation of the earth, as this would change its sign in the 

 opposite hemisphere, the deviating effects of this rotation, and of 

 the resistance of the air, would destroy each other, and there would 

 be no apparent deflection. 



Thus the influence of rotation on the deflection of projectiles 

 may become so considerable as to be taken into account, and to re- 

 ceive useful applications in artillery. — Comptes Rendus, Sept. 17, 1866. 



which the projectile falls from the trace of the plane of firing. Projectiles 

 generally deflect on the same side of the plane. The direction of the de- 

 flection depends on that of the screws and of the trace of the projectiles. 

 It is on the right for the guns used in the French army. 





