Dr. A. M. Mayer's Researches in Acoustics. 193 



Kohlrausch and Loomis, 1870. Pogg. Ann. 



Modulus of iron wire 5 per cent, less at 100° than at 0°. 

 Modulus of copper 6 per cent, less at 100° than at 0°. 

 Brass &2 per cent, less at 100° than at 0°. 



H. Tomlinson, 1887. Phil. Mag. xxiii. 



Says, "my own experiments show that both the torsional and 

 longitudinal elasticities of iron and steel are decreased by about 

 2 J per cent, when the temperature is raised from 0° to 100°." 



M. C. Noyes, 1895. The Physical Review. 



Modulus of a piano wire of ^ 4 q mm. diam. 5 per cent, less 

 at 100° than at 0°. 



The results of Wertheim's experiments giving an increase to 

 the modulus, as the temperature rises, of iron, iron wire, wire 

 of English cast-steel, steel wire drawn to blue, and silver, 

 have not been confirmed in any instance by subsequent 

 experiments ; only for cast-steel rod and copper did he obtain 

 a diminution of modulus for a rise of temperature from lb° 

 to 100°. Yet he found that a wire of English cast-steel had 

 a modulus 23 per cent, higher at 100° than at 18°. 



On the Acoustical Properties of Aluminium. 



The low density (2*7) of aluminium combined with a 

 modulus of elasticity of only 712 x 10 6 render this metal easy 

 to set in vibration ; a transverse blow given to a bar of this 

 metal causes it to vibrate with an amplitude of vibration 

 greater than that which the same energy of blow gives to a 

 similar bar of steel or of brass. This fact has given rise to 

 the popular opinion that aluminium has sonorous properties 

 greatly exceeding those of any other metal. This opinion is 

 erroneous. If a bar of aluminium and a bar of brass having 

 the same length and breadth and giving the same note, are 

 struck transversely so that the bars have the same amplitude 

 of vibration, the bars give equal initial intensity of sounds ; 

 but the bar of aluminium from its low density and because of 

 its internal friction will vibrate less than one-third as long as 

 the bar of brass. Thus, a bar of aluminium and a bar of brass 

 of the same length and width and of such thickness that they 

 gave the same note, SOL 4 of 768 v. d., were vibrated so that 

 the sounds at the moment of the blows were, as near as could 

 be judged, of the same intensity. The duration of the sound 

 of the brass bar was 100 seconds; the sound of the aluminium 

 bar lasted 30 seconds. 



The readiness with which a bar of aluminium vibrates when 

 acted on by aerial vibrations of the same frequency as those 



