Dr. A. M. Mayer's ResearcJies in Acoustics. 169 



except in the case of glass, where the computed is ^js below 

 the observed frequency. 



In Table I. I — length and t — thickness of bar in centimetres 

 at 20°; V = velocity of sound in centimetres in bar at 20° ; 

 N = number of vibrations per second at 20°. 



The close agreement of the computed and observed values 



shows that, by vibrating a bar at various temperatures, 



the variation of its modulus of elasticity with change in its 



temperature can be obtained. We observe N at various 



N 

 temperatures of the bar; then Y= is computed, 



1-0279 % 



Y 2 d 



and the modulus M= — . As t, l> and d (the density of 



the bar) vary with the temperature, the coefficient of 

 expansion of each bar and its density at 4° were determined, 

 so that the dimensions and density of the bar could be 

 computed for each of the temperatures at which it was 

 vibrated. 



Experiments were made on five bars of different steels, on 

 two of aluminium, on one of St. Gobain glass, one of brass, 

 one of bell-metal, one of zinc, and one of silver. The results 

 of these experiments may be summed up as follows : — 



The modulus of elasticity of St. Gobain glass is 1*16 per cent, less at 100° than at 0°. 



the five steels „ 2-24-309 



,, „ brass ,, 3*73 



„ „ bell-metal „ 4'3 



,, „ aluminium „ 5"5 



silver „ 2-47 „ „ 60 



zinc „ 604 „ „ 62 



The decrease of the modulus of elasticity of glass, aluminium, 

 and brass is proportional to the' increase of temperature; 

 straight lines referred to coordinates giving the results of 

 experiments on these substances. The five steels, silver, and 

 zinc give curves, convex upwards, showing that the modulus 

 decreases more rapidly than the increment of temperature ; 

 while bell-metal alone gives a curve which is concave 

 upwards, its modulus decreasing less than the increment of 

 temperature. (See Curves, fig. 5, p. 185.) 



The more carbon a steel contains, the less is the fall of its 

 modulus of elasticity on elevating the temperature of the 

 steel. Thus, the modulus of the steel with 1*286 per cent, of 

 carbon is 2'24 per cent, less at 100° than at 0°, while the 

 steel containing 0'15 per cent, of carbon has a modulus at 

 100° which is 3*09 per cent, lower than its modulus at 0°. 



So far as experiments on a single steel containing nickel 

 Phil. Mag. S. 5. Vol. 41. No. 250. March 1896. N 



