ocal organs as they
form sounds. Examines the Helmholtz method for the analysis
and synthesis of vocal sounds. Suggests the electrical actuation
of tuning-forks and the electrical transmission of their
tones. Distinguishes intermittent, pulsatory and undulatory
currents. Devises as his first articulating telephone a harp
of steel rods thrown into vibration by electro-magnetism.
Exhibits optically the vibrations of sound, using a preparation
of a human ear: is struck by the efficiency of a slight
aural membrane. Attaches a bit of clock spring to a piece
of goldbeater's skin, speaks to it, an audible message is
received at a distant and similar device. This contrivance
improved is shown at the Centennial Exhibition, Philadelphia,
1876. At first the same kind of instrument transmitted and
delivered, a message; soon two distinct instruments were
invented for transmitting and for receiving. Extremely small
magnets suffice. A single blade of grass forms a telephonic
circuit. 57

DAM, H. J. W.

PHOTOGRAPHING THE UNSEEN

Roentgen indebted to the researches of Faraday, Clerk-Maxwell,
Hertz, Lodge and Lenard. The human optic nerve is affected
by a very small range in the waves that exist in the ether.
Beyond the visible spectrum of common light are vibrations
which have long been known as heat or as photographically
active. Crookes in a vacuous bulb produced soft light from
high tension electricity. Lenard found that rays from a
Crookes' tube passed through substances opaque to common
light. Roentgen extended these experiments and used the rays
photographically, taking pictures of the bones of the hand
through living flesh, and so on. 87

ILES, GEORGE

THE WIRELESS TELEGRAPH

What may follow upon electric induction. Telegraphy to a
moving train. The Preece induction method; its limits.
Marconi's system. His precursors, Hertz, Onesti, Branly
and Lodge. The coherer and the vertical wire form the essence
of the apparatus. Wireless telegraphy at sea. 109

ILES, GEORGE

ELECTRICITY, WHAT ITS MASTERY MEANS: WITH A REVIEW AND A PROSPECT

Electricity does all that fire ever did, does it better,
and performs uncounted services impossible to flame. Its
mastery means