CHAPTER VIII 



THE SILENCE OF THE SEA AND THE VOICE 

 OF FISHES 



In the preceding pages a number of references to hearing have 

 been made and the auditory organs of fish have been described. 

 It may well be asked what are the sounds to be heard in the sea, 

 and also in rivers and inland waters. 



Although sounds are badly conducted from air to water, yet 

 sound is well conducted in water. During the Great War the locali- 

 sation of sounds produced by submarines was of outstanding im- 

 portance to our Navy, and a committee was set up to enquire into 

 the matter. I have heard it whispered that the scientists, which 

 included physicists and biologists, did not see eye to eye, or rather 

 ear to ear, in all the discussions that took place ; nevertheless, the 

 hydrophone was invented, and the experiments in the detection of 

 sounds in water were very successful and provided valuable aid 

 to the Admiralty in their efforts to combat the submarine menace. 



It is difficult for man, not being an aquatic animal, to project 

 his mind into the brain of a fish, nevertheless, by means of the 

 physiological methods, known as " conditioned reflexes," initiated 

 by Pavlov and applied by Bull to experiments on hearing in fish, 

 the subject has been put on a scientific basis. The ordinary man. 

 can reacUly prove for himself how well sounds are conducted in water 

 by immersing himself in a bath and listening to the ticking of a 

 clock or an electric buzzer placed under the water. 



To those who are unfamiliar with the subject, from the point of 

 view of a physicist, the simplest method of obtaining an outline of 

 the subject is to read the Christmas lectures, given at the Royal 

 Institution by Su- William Bragg, on the " World of Sound." 



Carlyle in another connection made use of the plu"ase " the deep 

 sea of Nescience," and it is a fact that the depths of the sea are very 

 silent. In the deep sea there is very little movement of water, 

 near the shore there is the fiow of the tides, and where waves break 

 there is noise because of the churning of the water into foam. 



The movements of fish are noiseless and even when sea-birds 

 dive and dart about under water no sound is audible, as experiments 



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