Sound / by John Tyndall.

  • John Tyndall
Date:
1883
Catalogue details

Licence: Public Domain Mark

Credit: Sound / by John Tyndall. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

    29/494 (page 7)
    BELL IN VACUO. Fig. 4. presence of this attenuated gas, though the receiver is now full of it. By working the pump, the atmosphere round the bell is rendered still more attenuated. In this way we obtain a vacuum more perfect than that of Boyle or Hawks- bee, and this is important, for it is the last traces of air that are chiefly effective in this ex- periment. You now see the hammer striking the bell, but you hear no sound. Even •when the ear is placed against the exhausted receiver, not the faintest tinkle is heard.. The bell is suspended by strings, for if it were allowed to rest upon the plate of the air-pump the vibrations would ^ be communicated to the plate, |§ and thence transmitted to the air outside. Permitting the air to re-enter the jar with as little noise as possible, you immediately hear a feeble sound, ■which grows louder as the air becomes more dense, until finally every person in this large assembly distinctly hears the ringing of the bell.1 Sir John Leslie found hydrogen singularly incompetent to act as the vehicle of the sound of a bell rung in the gas. More than this, he emptied a receiver like that be- fore you of half its air, and plainly heard the ringing of > By directing the team of an electric lamp on glass Lulbs filled with a mixture of equal volumes of chlorine and hydrogen, I have caused the bulbs to explode in vacuo and in air. The difference, though not so strik- ing as I at first expected, was perfectly distinct.