| 1st experiment | 15·34 |
| 2d experiment | 15·33 |
| 3d experiment | 15·34 |
Here the coincidence is quite as perfect as in the case of brass.
In glass, by this new mode of experiment, the velocity was found to be
15·25.[49]
Finally, in copper the velocity was found to be
11·96.
These results agree extremely well with those obtained by other methods. Wertheim, for example, found the velocity of sound in steel wire to be 15·108; M. Kundt finds it to be 15·34: Wertheim also found the velocity in copper to be 11·17; M. Kundt finds it to be 11·96. The differences are not greater than might be produced by differences in the materials employed by the two experimenters.
Fig. 111.
The length of the aërial column may or may not be an exact multiple of the wave-length, corresponding to the rod’s rate of vibration. If not, the dust segments usually take the form shown in Fig. 111. But if, by means of the stopper, b, the column of air be made an exact multiple of the wave-length, then the dust quits the vibrating segments altogether, and forms, as in Fig. 112, little isolated heaps at the nodes.