712
��Pojmlar Science Monthly
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��Mr. Berger's device resem- bles in principle the tomato- can toy. On the other hand, sounds sent out into the water
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��The signals sent out undLr the water are picked up by a microphone in the vessel
device. Is it not enough that men can signal through air with whistles and lights, through ether with wireless telegraphy, and over wires with the aid of electricity?
The answer is this: Strong as men have built ships, as well as they have chartered the ocean, as many safety devices as they have installed on boats, one overpowering danger still confronts navigators. That danger is fog. In a thick fog it is almost impossible to see from one end of a boat to the other, let alone out over the water toward any approaching vessels. Sound-signals do not carry far in air and are most un- trustworthy. Hcnco the freriucnt mis- haps which occur when bell-buoys, or other sound warnings near hidden reefs are not heard. Signal lights, rockets, lanterns, and similar de\'ict's depending upon light ari' obxiously inopcrati\e in a fog. Wireless waves — usually so cfTecl- ive in warnings of sea flangers — li.ne their limitations, too. Unless the op-
���erators carry on specific conversation as to their ships' positions and the danger of biniiping into each other or into objects on shore, the wireless signals them- selves carry no warning of impending disasters; the strength of wireless sig- nals, as received, is no criterion of the sending ve-ssel's distance.
Hence when a fog descends over the sea, light signals are utterly useless, sound signals in air do not carry far and are uncertain, and wireless telegraphy is good onl\- in certain instances. Is it any wonder that inxenlors have taken to iiixestigating the possibilities of sub- marine signaling, all the more since they have discovered that sountl -signals will carr\- long distances under water and are unalTected by fogs and storms?
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