Page:Tactics (Balck 1915).djvu/208

 Let A B B', in the accompanying figure, represent a horizontal plane pierced by trajectories C B and C' B', at an angle a, forming the beaten zone B B'. If now the ground falls from B in the direction B D, it is obvious from the figure, that the angle of fall decreases and the beaten zone B D increases. The limit of this increase is reached when the angle of slope is greater than the angle of fall of the projectile. In this case there is a dead angle beyond B and toward D. If, on the other hand, the ground be rising, the angle of fall will be C' D' B and the beaten zone decreases to B D'. The smaller the angle of fall of the projectile the greater the influence of the ground.

From this it follows that when fire direction is in competent hands the appearance of the enemy on the terrain as at B D will be fully taken advantage of, while firing on slope like B D' should be avoided. Troops will, however, rarely be in a position from which they can see a target on the slope B D. The efficacy of the fire will in such a case be more or less= angle of slope (rising or falling); b = beaten zone on level ground; then a/(a - [Greek: g])b))b] = beaten zone on falling ground; a/(a + [Greek: g])b + [Greek: g]))[Greek: b]] = beaten zone on rising ground. ]