I must assume that my readers are familiar with the receiving apparatus of wireless telegraphy, which must be "tuned" by the operator until its own vibratory quality is in exact harmony with the vibrations--the extremely rapid impacts--of those short electric wavelengths we call Hertzian, and which carry the wireless messages.

I must assume also that they are familiar with the elementary fact of physics that the vibrations of light and sound are interchangeable.
The hearing-talking globes utilize both these principles, and with consummate simplicity.

The light with which they shone was produced by an atomic "motor" within their base, similar to that which activated the merely illuminating globes.

The composition of the phonic spheres gave their surfaces an acute sensitivity and resonance.

In conjunction with its energizing power, the metal set up what is called a "field of force," which linked it with every particle of its kind no matter how distant.