The telescope is then turned so it is vertical, as at C, and the observer watches through the telescope until the machine passes directly over the object, when the watch is stopped, to indicate the time between the two observations.
Fig. 91. Determining Altitude and Speed.
The height of the machine along the line D is thus equal to the line E from B to C, and the time of the flight from B to a being thus known, as well as the height of the machine, the observer consults specially-prepared tables which show just what kind of a curve the bomb will make at that height and speed.
All that is necessary now is to set the sighter of the telescope at the angle given in the tables, and when the object to be hit appears at the sight, the bomb is dropped.
THE GREAT EXTENT OF MODERN BATTLE LINES.— The great war brought into the field such stupendous masses of men that the battle lines have extended over an unbroken front of over 200 miles.
In the battle of Waterloo, about 140,000 men were engaged on both sides, and the battle front was less than six miles. There were, thus massed, along the front, over 20,000 men every mile of the way, or 10,000 on each side.
In the conflict between the Allies and the Germans it is estimated that there were less than 7500 along each mile. It was predicted in the earlier stages of the war that it would be an easy matter for either side to suddenly mass such an overwhelming force at one point as to enable the attacking party to go through the opposing force like a wedge.
Such tactics were often employed by Napoleon and other great masters of war; but in every effort where it has been attempted in the present conflict, it was foiled.
The opposing force was ready to meet the attack with equal or superior numbers. The eye of the army, the aeroplane, detected the movements in every instance.
THE AEROPLANE DETECTING THE MOVEMENTS OF ARMIES.—In the early stages of the war, when the Germans drove the left of the French army towards Paris, the world expected an investment of that city. Suddenly, and for no apparent reason, the German right was forced back and commenced to retreat.