uthority on matters of electrical
communication. It was he who contributed so largely to the success of
the early telegraph cable system between England and America. Two of
his comments which are characteristic are as follows:

To-day I have seen that which yesterday I should have deemed
impossible. Soon lovers will whisper their secrets over an
electric wire.

* * * * *

Who can but admire the hardihood of invention which devised such
slight means to realize the mathematical conception that if
electricity is to convey all the delicacies of sound which
distinguish articulate speech, the strength of its current must
vary continuously as nearly as may be in simple proportion to the
velocity of a particle of the air engaged in constituting the
sound.

Contrary to usual methods of improving a new art, the earliest
improvement of the telephone simplified it. The diaphragms became thin
iron disks, instead of membranes carrying iron; the electromagnet
cores were made of permanently magnetized steel instead of temporarily
magnetized soft iron, and the battery was omitted from the line. The
undulatory current in a system of two such telephones joined by a line
is _produced_ in the sending telephone by the vibration of the iron
diaphragm. The vibration of the diaphragm in the receiving telephone
is _produced_ by the undulatory current. Sound is _produced_ by the
vibration of the diaphragm of the receiving telephone.

Such a telephone is at once the simplest known form of electric
generator or motor for alternating currents. It is capable of
translating motion into current or current into motion through a wide
range of frequencies. It is not known that there is any frequency of
alternating current which it is not capable of producing and
translating. It can produce and translate currents of greater
complexity than any other existing electrical machine.

Though possessing these admirable qualities as an electrical machine,
the simple electromagnetic telephone had not the ability to transmit
speech loudly enough for all practical uses. Transmitters producing
stronger telephonic currents were developed soon after the fundamental
invention. Some forms of these were invented by Professor Bell
himself. Other inventors contributed devices embodying the use of
carbon as a resistance to be varied by the motions of the diaphragm.
This general form