We learn from this table that sound travels with different velocities through different liquids; that a salt dissolved in water augments the velocity, and that the salt which produces the greatest augmentation is chloride of calcium. The experiments also teach us that in water, as in air, the velocity augments with the temperature. At a temperature of 15° C., for example, the velocity in Seine water is 4,714 feet, at 30° it is 5,013 feet, and at 60° 5,657 feet a second.
I have said that from the compressibility of a liquid, determined by proper measurements, the velocity of sound through the liquid may be deduced. Conversely, from the velocity of sound in a liquid, the compressibility of the liquid may be deduced. Wertheim compared a series of compressibilities deduced from his experiments on sound with a similar series obtained directly by M. Grassi. The agreement of both, exhibited in the following table, is a strong confirmation of the accuracy of the method pursued by Wertheim:
| Cubic compressibility | ||
| ╭———————^———————╮ | ||
| from Wertheim’s velocity of sound | from the direct experiments of M. Grassi | |
| Sea-water | 0·0000467 | 0·0000436 |
| Solution of common salt | 0·0000349 | 0·0000321 |
| ” carbonate of soda | 0·0000337 | 0·0000297 |
| ” nitrate of soda | 0·0000301 | 0·0000295 |
| Absolute alcohol | 0·0000947 | 0·0000991 |
| Sulphuric ether | 0·0001002 | 0·0001110 |
The greater the resistance which a liquid offers to compression, the more promptly and forcibly will it return to its original volume after it has been compressed. The less the compressibility, therefore, the greater is the elasticity, and consequently, other things being equal, the greater the velocity of sound through the liquid.
We have now to examine the transmission of sound through solids. Here, as a general rule, the elasticity, as compared with the density, is greater than in liquids, and consequently the propagation of sound is more rapid.
In the following table the velocity of sound through various metals, as determined by Wertheim, is recorded:
Velocity of Sound through Metals
| Name of Metal | At 20° C. | At 100° C. | At 200° C. |
| Lead | 4,030 | 3,951 | ...... |
| Gold | 5,717 | 5,640 | 5,619 |
| Silver | 8,553 | 8,658 | 8,127 |
| Copper | 11,666 | 10,802 | 9,690 |
| Platinum | 8,815 | 8,437 | 8,079 |
| Iron | 16,822 | 17,386 | 15,483 |
| Iron wire (ordinary) | 16,130 | 16,728 | ...... |
| Cast steel | 16,357 | 16,153 | 15,709 |
| Steel wire (English) | 15,470 | 17,201 | 16,394 |
| Steel wire | 16,023 | 16,443 | ...... |
As a general rule, the velocity of sound through metals is diminished by augmented temperature; iron is, however, a striking exception to this rule, but it is only within certain limits an exception. While, for example, a rise of temperature from 20° to 100° C. in the case of copper causes the velocity to fall from 11,666 to 10,802, the same rise produces in the case of iron an increase of velocity from 16,822 to 17,386. Between 100° and 200°, however, we see that iron falls from the last figure to 15,483. In iron, therefore, up to a certain point, the elasticity is augmented by heat; beyond that point it is lowered. Silver is also an example of the same kind.