84 A. M. Mayer — Researches in Acoustics. 



A bar of unannealed drawn brass, after it has been heated to 

 100°, has its modulus increased -££$ per cent. See Table III 

 and ftg. 11, p. 98. 



In this research I had the good fortune to have had the 

 assistance of Dr. Rudolph Kcenig, of Paris. He not only 

 placed at my service the resources of his laboratory and work- 

 shop, but generously gave me constant assistance during the 

 experiments ; making the determinations of the numbers of 

 vibration of the rods and bars with the standard forks of his- 

 tonometer. Without his aid this work could not have been 

 done. For instance, in the cases of the bars of silver and zinc 

 the beats they give with a fork are so few that they cannot be 

 compared with a chronometer ; but Dr. Koenig, from his long 

 experience in the estimation of beats, was enabled to form an 

 accurate judgment of their number per second from the 

 rhythm of the beats. The determination of pitches extending 

 through such a range of vibrations as occur in this research 

 can only be made with Dr. Koenig's u grand tonometre," a 

 unique apparatus of precision, giving the frequency of vibra- 

 tions from 32 to 43690 v. s., and really indispensable to the 

 physicist who would engage in precise quantitative work in 

 acoustics. 



We now proceed to give accounts of the several operations 

 performed in the progress of this research. 



Determination of the Velocity of /Sound in Hods. 



In the determinations of the velocity of sound in the rods of 

 1*5 m. in length I used the method of Chladni.* Kundt's 

 method of obtaining nodal lines of tine powders in a tube, by 

 vibrating a rod whose end carries a cork which fits loosely the 

 end of the tube, is not accurate. The weight and friction of 

 the cork, the necessity of firmly clamping the rod at a node, 

 and, above all, the want of knowledge of the velocity of sound 

 in the air of glass tubes of different diameters, renders this 

 method, so beautiful and ingenious, worthless for accurate 

 measures of the velocity of sound in solids. 



The curves in fig. 1 show the very diverse determinations 

 of the velocity of sound in the air in tubes of different diam- 

 eters by the physicists Kundtf, SchneebeliJ, Seebeck§, and 

 Keyser||. The velocity of sound in metres is given on the 

 axis of "Y ; the diameter of the tube in centimeters on the axis 

 of X. Ku stands for Kundt, Sch for Schneebeli, Se for See- 

 beck, and Ke for Keyser. The most precise measures of 



* Traite d'Acoustique, Paris, 1809, p. 318 et seq. 



+ Bericht. der Akad. der Wiss. zu Berlin. 1861. 



% Pogg. Ann.. 1869, vol. cxxxvi. . § Pogg. Ann., 1870, vol. cxxxix. 



I Wied. Ann., 1877, vol. ii, p. 218. 



