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



box had been condensed so far as it could be at 0°. The bar, 

 which had been in ice for two hours, was wiped dry and quickly 

 introduced into the inner box. A thermometer, T (made by 

 Baudin and corrected), which entered the boxes through 

 stuffing-boxes, and whose bulb touched the under surface of 

 the bar, was read till it became stationary. The bar was now 

 vibrated, and its frequency of vibration determined for the 

 temperature given by the thermometer. 



The lamp was now placed under the box, and the water in 

 it boiled till the thermometer reached its maximum reading 

 and the reading remained stationary during a half-hour. 

 The vibration frequency at this temperature was taken. The 

 flame of the lamp was now lowered and the box allowed to 

 cool very slowly, at the rate of 1° fall of temperature in about 

 eight minutes. When the thermometer read 80°, 60°, 40°, 

 the flame of the lamp was carefully adjusted, so that these 

 successive temperatures were maintained during 15 minutes. 

 We then took the frequency of vibration of the bar. 



The numbers of vibrations of the forks used in the deter- 

 minations of the pitches of the bars were corrected for tem- 

 perature by the coefficient '0001118, determined by Dr. Koenig 

 in 1880 (Quelques Experiences d'Acoustique, Paris, 1882, 

 p. 172 et seq.). 



The subsequent tables show the results of the experiments 

 and give the computations of velocities and moduli founded 

 on them. The curves express graphically the effect of change 

 of temperature on the modulus of elasticity of all the bars 

 experimented on. The circles, on or near the curves, give 

 the data as determined by the experiments. 



In Table III., T = temperature of bars, Z = the length, £ = the 

 thickness, and V = the velocity of sound through the bars, in 

 centimetres. M = the modulus in grammes per square centi- 

 metre section of the bar. g, at Paris, equals 980*96. D = the 

 density, and N=the number of vibrations of bar per second 

 at temperature, T. 



All of the bars were annealed, except those of Jonas and 

 Colver steel, of the French aluminium, and of brass ; these 

 were experimented on just as they came from the draw-bench. 



For the analyses of the substances of the bars experi- 

 mented on, I am indebted to my colleagues, Professors 

 Stillman and Leeds. 



