RESEARCHES IN RADIOTELEGRAPHY.¢ 
(With 2 plates.) 
By cerot, Ja A] HiEeMminG) MeeA DD: Se: Bo Revs: 
Radiotelegraphy, popularly called wireless telegraphy, has out- 
lived the tentative achievements of its precocious infancy and obtained 
for itself a settled but important position amongst our means of 
communication. 
This stage, however, has only been reached after a long struggle 
with experimental difficulties and much labor in analyzing the proc- 
esses involved. As many of these matters are of general scientific 
interest, it is proposed, during the present hour, briefly to summarize 
the results of some recent research. 
You are doubtless all aware that every radiotelegraphic station 
comprises three elements. There is, first, the external organ called the 
air wire or antenna, by which the electromagnetic waves are radiated 
and absorbed. This antenna consists of one or more wires extending 
up into the air, either vertically or sloping, or partly vertical and 
partly horizontal. These wires are insulated at the upper ends and 
may be arranged fan fashion, or may form one or more nearly closed 
loops, placed in a vertical position. The antenna is, so to speak, the 
mouth or ear of the station, by which it speaks through the ether, or 
by which it hears the etherial whispers coming to it from other 
stations. The ether waves are produced by very rapid electric cur- 
rents moving to and fro in the antenna wires, and these, like the 
vibrations of a violin string, or the aerial oscillations in an organ 
pipe, set up a periodic disturbance in the surrounding medium, which 
in the electrical case consists of alternating electric and magnetic 
forces taking place at each point in space around the antenna. 
There are, then, appliances in the station collectively called the 
transmitter, which have for their function to create these powerful 
electric oscillations in the antenna, and to control them so as to send 
out short or long trains of ether waves in accordance with the dot or 
dash signals of the Morse alphabet. Lastly, there is the receiving 
@QVecture before the Royal Institution of Great Britain, Friday, June 4, 1909. 
Reprinted by permission from pamphlet copy published by the Royal Institution. 
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