Perhaps the greatest invention of the modern age in importance, after the atomic bomb, is that invention known as radar. Thanks to it, the lives of thousands of fighting men and civilians were saved; for by its means attacking aircraft can be detected while they are still hundreds of miles from their targets, and thus one can prepare for them, guard against their dangers, and stand firm against them while they are still far, far away. This wondrous radar is nothing other than a short wireless wave sent out from the defending shores; it crosses the distances with the speed of lightning, and no sooner does it strike something solid than it is reflected and returns the way it came, so that its senders can take the measure of the distance separating them from that solid object, be it an airplane, a battleship, or anything else. Those who know foresee important benefits from this invention in peacetime, for by its means the danger disappears of collisions between aircraft, or warships, or steamers, or automobiles, in fog or in darkness; and so travel becomes little exposed to the dangers arising from these causes.

This is what man arrived at, after immense and mighty efforts, in the present age. Yet the bat — that nocturnal bird, if you care so to call it — has been equipped with this invention ever since it came into being; it is part of its very frame, as our eyes are part of us, guarding it against the dangers of colliding by night with the obstacles in its way. This secret in the bat was discovered by Professor Hartridge of London, after he had spent twenty years trying to learn the secret by which the bat manages to hunt insects and to avoid collisions while flying through the blackest dark of night.

He was guided to this discovery by his observation that deaf bats collide with the obstacles arising before them, while blind

ones that hear well do not collide. From this he concluded that the bat avoids stumbling by means of its ears, not by means of its eyes — that is, it makes its way and escapes collision with its ears, not with its eyes. Research and inquiry led him at last to the discovery of the principle of radar in the body of the night-flying bird. And here is the account of it:

When the bat flies, the vibrations of its vocal cords issue through its nose (just as the wireless waves issue from the radar) and go spreading out in every

direction; and no sooner do they strike something solid, be it small or large, than they are reflected back again, and its two great ears pick them up (just as we pick up an echo); they act upon its nervous system, so that it senses the presence of the smallest things and their direction, and avoids them. Scientists have been able to record these vibrations issuing from the bat in the laboratory.

It is related of Professor Hartridge that he said in this connection:

"I was the first to discover the principle of radar, through my studies of the bat; but nature knew it thousands of years before me, and perfected its workmanship in the bat."