23.2 Intelligence and Miscellaneous Articles. 



tubes used. The observations were reduced to zero by means of the 



formula X = , x , by observing at the commencement and the 



Vl + af 



end of each series of observations a thermometer placed close at 

 hand : the air in the tube was first dried by chloride of calcium. 

 Seebeck used Konig's four tuning-forks, which give the notes ut v 

 sol 3 , mi z , ut 3 , of which the numbers of vibrations were 512, 384, 320, 

 256. He found the following results : — 



Tuning-forks. 



Diameter. f A — > 



2r. ut 3 =256. wt 8 = 320. sol 3 =384. w* 4 =512. 



millims. millims. millims. millims. millims. 



3*4 .. 317-26 318-86 322-98 



9 325'63 327-22 327*68 328-44 



17-5 327-82 329-24 329*86 330-92 



29 324-54 325*36 326*72 326*10 



The velocity of the sound diminishes with the diameter of the tube, 

 except for the largest (2r= 29 millims.), which Seebeck attributes 

 to the whole of the section not having been agitated ; it may also 

 be that in the large tubes the motion of the gaseous molecules is not 

 parallel to their axis. By adopting for the velocity of sound in air 

 a the number 332*77 millims., a result obtained from the determina- 

 tions by Moll and Van Beek, Seebeck has calculated the difference 

 A — V. According to the formula by Kirchhoff, we must have 



A-V-A. * 



2rVmr 



and consequently, for the same sound and various tubes, 

 (A-V 1 )x2r 1 =(A-V 2 )x2r 2 , 



an equation which the determinations of Seebeck satisfy, except for 

 the largest tube (2r=29 millims.). But it was also found that 

 (A— V) V^j f° r the same value of r, is no longer constant. Seebeck 

 recognized, on the contrary, that the product (A— V)?i2 was ob- 

 viously constant ; and consequently the diminution of velocity of 

 sound in a tube varies in inverse ratio with the power -| of the num- 

 ber of vibrations of the corresponding sound. 



Seebeck also made some investigations when the interior of his 

 tubes was covered with leather or flannel : he proved that there was 

 a considerable diminution in the velocity of sound ; in the latter case 

 it fell to 281*7 millims. These experiments, however, leave some- 

 thing to be desired, because the interior of the tube was not com- 

 pletely covered. A small slit was made that the position of the 

 piston might be observed : would it not be possible to determine the 

 position of the piston exactly by means of the rod by which it is re- 

 gulated? — PoggendorfFs Annalen, vol. cxxxix. p. 104; Annates de 

 Chimie, April 1870. 



