A New System for Preventing Collisions at Sea 



humming bird also moves its wings with sufficient rapidity to 

 produce an audible musical note. In many kinds of beetles, 

 the wings are not moved rapidly enough to produce an 

 audible note, but every insect or bird that flies does produce 

 atmospheric vibrations which are identical with sound and 

 are governed by the same laws, the only difference being that 

 the formation of our ears is such that they are unable to 

 respond to such very low notes. This, however, does not 

 prove their non-existence ; it shows rather the limitation of 

 our ears. It requires sixteen pulsations or vibrations of the 

 air in a second of time to produce the deepest bass note 

 that we are able to hear and which corresponds to the note 

 given off by a 32-foot organ pipe. 



As a rule, the bats that are provided with the sixth sense 

 are very small, and it is probable that they only make about 

 ten to twelve strokes with their wings in a second of time. 

 This, of course, produces an extremely low note that does 

 not appeal to our ears, but it travels after the manner of 

 sound or light, for that matter strikes all of the surround- 

 ing objects, becomes modified by their character and size, 

 and is reflected back, and these reflections or echoes are 

 received by the organ of the sixth sense and analysed, exactly 

 the same as light waves would be by our eyes under 

 similar conditions. It is, therefore, certain that the bat obtains 

 its knowledge of surrounding objects by sending out certain 

 atmospheric vibrations and receiving back in a fraction of a 

 second later, the reflected and modified vibrations. 



This is a purely mechanical problem. From the foregoing, I 

 think its action will be understood, and I do not think it will 

 be denied that we can imitate it to some extent mechanically. 



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