8o Journal of Comparative Neurology and Psychology. 



exact methods of study of mental traits in relation to education, and 

 this is more than justification for its appearance at this time. 



H. HEATH BAWDEN. 



Are Sounds, Made in the Air, Audible in the Water? 



In their works on the sense of hearing in fishes and Crustacea, 

 Kreidl, Bker and Parker have laid more or less emphasis on the 

 reflection of sound waves in the air from the surface of the water. 

 Parker says (basing his statement to some extent upon experiment), 

 "the plane separating air and water is, under ordinary circumstances, 

 an almost impenetrable one for most sounds, whether they are gene- 

 rated on one side or the other of it, and many of the negative results 

 obtained by previous investigators on the sense of hearing in fishes 

 may have been due not so much to the absence of hearing in the ani- 

 mals experimented upon as to their inaccessibility to the sound, or at 

 least to sound of an intensity sufficient to stimulate." 



Interesting experimental evidence on this question is furnished by 

 Dr. V. DuccESCHi,' of Naples, in a recent number of the Rivista 

 d' Italia. Struck by the fact that some boys, diving along the shore, 

 were able to repeat, on emerging from the water, the words called to 

 them by their comrades while they were sdll beneath the surface, he 

 secured the services of an expert diver, provided himself with a boat 

 and some simple apparatus, and set out to test the matter experiment- 

 ally. Trials were made at various depths up to seven meters. The 

 length of time that the diver remained under water was about lo seconds. 

 At 5 meters the diver could hear distinctly, and rei)eat on coming to 

 the surface, every word called to him from the boat. At 6 meters he 

 could distinguish between the sounds of two glass bells of different 

 sizes, a whistle and a small trumpet, all sounded in the air, could tell 

 how many times each one was sounded, and in what order. At 7 

 meters the diver was able to distinguish the sounds with much less cer- 

 tainty, and sometimes not at all. The high tones were found to be 

 much more difficult to distinguish than the low. 



I'he same set of experiments was tried when the water was some- 

 what rough, with the result that the sounds were perceived with slightly 

 less accuracy. It is true that in all these experiments the possibility of 

 the sound being communicated through the boat to the water is not ex- 

 cluded. Moreover Ducceschi thinks it may be a question whether 



IV. Ducceschi. Gli animali aquatici possiedono il senso dell 'udito? 

 Rivista (V Italia, Anno VI, pp. 958-966, Dec, 1903. 



