Dr. A. M. Mayer's Researches in Acoustics. 171 



workshop, 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 occurs in this 

 research can only be made with Dr. Koenig's " grand tono- 

 metre " — a unique apparatus of precision, giving the fre- 

 quency of vibrations 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 Rods. 



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 fine 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 dia- 

 meters by the physicists Kundtf, Schneebeli J, Seebeck§, 

 and Kayser |] . The velocity of sound in metres is given on 

 the axis of Y ; the diameter of the tube in centimetres on the 

 axis of X. Ku stands for Knndt, Sch for Schneebeli, Se for 

 Seebeck, and Ke for Kayser. The most precise measures of 

 velocities are those of Kayser, who closed the end of the tube 

 with a cork attached to the end of a steel bar, while the other 

 end of the bar was securely clamped. The frequency of the 

 transverse vibrations of the bar was registered by a style 



* Traite dAcoustique, Paris, 1809, p. 318 et seq. 



t Bericht. der Akad. der Wiss. zu Berlin, 1867. 



t Fogg. Ann. 1869, t. 136. § Yogg. Ann. 1870, t. 139. 



|| Pogg. Ann. 1877, t. 2. p. 218. 



N2 



