164 Dr. E. Warburg on the Deadening of the Sounds 



sound and the ear, nothing more could be perceived of the higher 

 notes, while the deep accompaniment was perfectly distinct. 



A slightly stretched hemp cord4'5 metres in length exhibited 

 the same deportment as the caoutchouc and the longer lead con- 

 ductor; when it was somewhat more tightly stretched, the higher 

 notes were superadded to the lower ones ; the caoutchouc rod, 

 on the contrary, had to be very strongly stretched (that is, drawn 

 out to about three times the length) for the highest tones to 

 be propagated in it to somewhat greater distances. 



Connected with these experiments is the unequal enfeeble- 

 ment which notes of various height undergo on conduction 

 through the air which is enclosed in caoutchouc tubes. Near to 

 that end of a wooden rod connected with the musical box which 

 projected from the water, one end of an open glass tube was ap- 

 proached. When the other end of the tube was introduced into 

 the ear, the entire piece of music was heard, with the exception 

 that, especially with short tubes, certain notes were rendered par- 

 ticularly prominent by resonance. When the glass tube was re- 

 placed by a caoutchouc tube, provided the length of the conduction 

 was adequate, only the deeper notes could be perceived. For the 

 same thickness of the sides of the caoutchouc tubes, the enfeeble- 

 ment of the tones on conduction, especially of the higher ones, 

 diminishes with a decrease in the internal diameter. To show 

 this, it is sufficient to introduce simultaneously into the two ears 

 two tubes of different diameters, and to bring the free ends near 

 the source of sound. If now either one or the other tube be 

 compressed, the difference in the strength and composition of the 

 sound propagated by the two conductions can be judged, and it 

 will be ascertained that the higher tones pass more readily through 

 the narrow tube than through the wider. 



This deportment shows that the enfeeblement of sound in these 

 experiments must first of all be ascribed to imperfect reflection 

 from the caoutchouc sides ; for, ceteris paribus, they yield to a 

 greater extent the greater the internal diameter of the tube. It 

 was therefore to be expected that a considerable degree of sound 

 was to be imparted by conduction to the external air, of which the 

 author has convinced himself by special experiments. 



We must accordingly conceive the conduction through air in 

 caoutchouc tubes to take place by the caoutchouc tube being 

 made to vibrate transversely by the vibrations of the air. These 

 transversal vibrations of the solid caoutchouc are enfeebled as 

 they advance, and, according to the experiments first described, 

 the higher-tone vibrations much more rapidly than the deeper 

 ones. Hence the higher tones are lost from the system more 

 rapidly than the lower ones, and the deeper ones are maintained 

 for a longer time. The question remains open whether also there 



