The ear, too, has not done so well from the point of view of artificialmultiplication. But it has a more interesting record than the nose, for there are quite a number of inventions which have no other purpose than the unlimited renforcement of the power of hearing.Most of these are of very recent origin and consist of artificially constructed ears which are able to catch the noise made by an aeroplane propeller long before their human counterpart has noticed anything out of the usual.No doubt the development of aircraft will force us to pay more and more attention to the art of long-distance listening.But until a dozen or so years ago, we were trying to listen intensively rather than extensively and the few original inventions connected with the ear all show their common origin and purpose.

It would of course be possible to argue that the telephone and radio should be classified under this chapter heading. A good case could also be made out for the loud-speaker as an amplified ear.But I believe that properly speaking all these instruments belong to the mouth.Their main purpose is to“tell”something at a distance.The speaking end, therefore(the mouth),is enormously magnified while the ear as the organ of hearing is left practically as it was before.Until I am definitely shown that I am wrong I shall therefore leave them where they are, and here I shall mention only such inventions as are a direct outcome of our necessity to hear-with-greater-precision.

Water being an excellent conductor of sound, it was quite natural that the value of the multiplied ear should have first been realized by the men of the sea. Already the Norsemen seem to have known that when one hit the walls of a wooden ship below the water-line, the sound could be heard quite a distance away by those who had their ears glued to the side of their own vessel at some spot a few feet below the level of the sea.Even to-day in certain parts of the northern Atlantic in case of fog, sailing ships that have been becalmed and wish to remain close together communicate with each other by means of tapping the sides of their vessels.

This method, however, would be a little too primitive for large ocean steamers and they have increased their power of hearing with different electrical devices which perform a number of tasks formerly entrusted to the hand or to the eye, such as finding out how deep the water is or whether there are any hidden rocks or whether the vessel is approaching land.

On shore there is no need of such instruments. Even if there were it is doubtful whether they could be used amidst the conflicting noises of our modern cities.But in the quiet of his room.the physician, renforcing his car with a stethoscope, is now able to listen to a number of things that formerly were completely out of reach of both his eyes and his hands and along that line we may probably look for further developments of great value.

There may be other instruments that are merely multiplications of the power of hearing. But I do not know what they are.

But I hope that they won't mention the dictaphone, for somehow or other that useful implement of high-class sleuthing does not seem to fit into this book. I know that it exists and plays a great r1e in the lives of all movie detectives, giving them an opportunity to frustrate plots and expose counterfeiters.But somehow or other it does not seem to belong in a book that is chiefly devoted to a chronicle of human progress.