706 



Prof. J. E. Ives on the Absorption of 



rubber cylinder ; m, cross-section of parabolic mirror of 

 sheet zinc ; and d, the wooden support. 



According to the experiments of Weber * and others, the 

 wave-length of the waves emitted by the sender would be 

 changed during their passage through the tubes, owing to 

 the fact that a tube has a natural vibration of its own. 

 According to Weber, the wave-length of the free vibrations 

 in a tube is equal to 3*415 times the radius of the tube. 

 In this case, therefore, the length of the waves due to the 

 free vibrations of the tubes would be 17 cm. So that even 

 if the length of the waves, due to the sender, was changed 

 in passing through the tube, it would still be short. 



Ri and R 2 (fig. 1) were the receivers. They were each 

 4*4 cm. long, and made of two pieces of copper wire 

 *0285 cm. in diameter joined together by a thermoelectric 

 junction made of iron and constantan wires, each *0208 mm. 

 in diameter, soldered at the junction. The wires going 

 from the junction to the galvanometer were led out side by 

 side through the centre of its wooden support. The fine 

 wires forming the junction had a total length of about 4 mm. 



Fig. 3. 



8 



,-3 



a 



--a 



Receiver. A. front view : B. side view. 



The receiver is shown in detail in fig. 3, where A is a 

 front view and B is a side view, aa are the copper wires 



* Ann. Phys. viii. p. 743 (1902). 



