Inventions of the Great War

ng th

nder. He may not know it, but he is, just the same, and the way

. It is not quite fair to have a bird's-eye view of the field, so get down on your knees and bring your eyes within a few inches of the top of the table. Now close one eye and making your hand describe an arc through the air, like the arc that a shell would describe, see how nearly you can bring the pencil-point down on t

u are not a good range-finder; but now use two eyes and you will score a hit every time. Not only can y

y are turned in, and the farther the object, the more nearly parallel are the eyes. Long experience has taught you to gage the distance of an object by the feel of the eyes-that is, by the effort your muscles have to make to pull

o which you can gage the range. At a distance of, say, fifteen or twenty feet, a variation of a few inches beyond or this side of the target makes scarcely any

THE EYES

ms makes this possible. The range-finder may be a yard or more in length, which is equivalent to spreading your eyes a yard or more apart. Now, the prisms or object-glasses at the ends of the tube are adjustable, so that they will turn in until they focus directly on the target whose range you wish to find, and the angle through which these glasses are turned gives a measure of the distance of the target. The whole thing is calculated out so

is necessary to get the range of a very distant object, two observers are used who are stationed several hundred yards apart. These observers have telescopes which they bear upon the object, and the angle through which they have to turn the telescope is reported by telephone to the battery, where, by a rapid calculation, it is possible to estimate the

OBSERVER O

gh. But the great European conflict brought out wonderful improvements in all branches of fighting; and range-finding was absolutely

g air-bag that curls around the lower end of the sausage. This acts like a rudder, and steadies the balloon. Some balloons have a tail consisting of a series of cone-shaped cups strung on a cable. A kite balloon will ride steadily in a wind that would dash a common round balloon in all directions. Observers in these kite balloons are provided with telephone instruments by which they can communicate instantly with the battery whose fire they are directing. But a kite balloon is a helpless object; it cannot fight the enemy. The hydrogen gas that holds it up will burn furiously if set on fire. In the war an

nd, our army was preparing to use balloons that were not afraid of flamin

APS WITH

placed in dugouts so that they could not be located. Such targets could seldom be found with a kite balloon. It was the task of airplane observers to search out these hidden batteries. The eye alone was not depended upon to find them. Large cam

rwood &

Section getting the Ra

As the enemy was always careful to disguise its work, the camera had to be fitted with color-screens which would enable it to pick out details that would not be evident to the eye. As new photographic maps were made from day to day, they were carefully compare

del &

aking Observations

TING T

the shell. If the shell traveled through a vacuum, it would be a much simpler matter to score a hit by the map alone. But even then there would be some differences, because a gun has to be "warmed up" before it will fire according to calculation. That is why it is necessary to have observers, or "spotters" as they are called, to see where the shell actually do lan

fifty miles. With the wireless telephone, the observer could communicate instantly with the gun-pointer, and tell him when to fire. Usually thirty seconds were allowed after the signal sent by the observer before the gun was fired, and on the instant of firing, a signal was sent to the man in the airp

shell was to land. Then he would look for the column of smoke produced by the explosion of the shell and report back to the battery how far wide of the mark the shell ha

to be buried deep in the ground before exploding, so as to destroy dugouts and underground positions. The bursts of smoke from the delayed-action shell and the semi-delayed-action shell rise in a slender vertical column and are not so easily seen from the sky. The instantaneous shell, however, produces a broad burst of smoke which

RE BATT

ould get a bird's-eye view of the territory represented on the map, and they were connected by telephone or telegraph with men below who represented the batteries. The instructor would flash a little electric light here and there on the miniature battle-field, and the observers had to locate these flashes and tell instantly how far they were from certain targ

ING B

essage is picked up by a recorder at several different receiving-stations. Of course it reaches the nearest station a fraction of a second before it arrives at the next nearest one. The distance of each station from the target is known by careful measurement on the map, and the time it takes for sound to travel from the target to each station is accurately worked out. If the sound arrives

pt the flash at the instant of discharge, and even the flash was hidden by screens from the view of an airplane. Aside from this, when an airplane came near enough actually to see one of these guns, the gun would stop firi

all, the main responsibility for good shooting had to fall on observers who could actually see the target, and when we think of the splendid work of our soldiers in the war, we must not forget to give full credit to the tireless men whose duty it was to watch, to the men on wings who dare