ELECTRIC WAVE TELEGRAPHY—FLEMING. 187 
case the necessary modulation was impressed upon the radiated elec- 
tric waves by inserting the primary circuit of an induction coil in the 
continuous current arc circuit, and closing its secondary through a 
microphone transmitter and working battery. The receiving ar- 
rangement involved an electrolytic receiver as just described. Pro- 
fessor Fessenden has recently described very similar arrangements 
for electric wave wireless telephony.*. We can, however, say that 
something more than a beginning has been made in the art of the 
wireless transmission of human speech to a distance. The energy ex- 
penditure is at present considerable, and much will have to be done 
before telephony without wires can be looked upon as coming within 
the range of commercial work. Nevertheless, having regard to the 
enormous improvements in wireless telegraphy in the last seven years, 
it is quite within the bounds of possibility we may soon be able to 
speak across the English Channel without a wire, and not scientific- 
ally impossible for the sounds of the human voice to be some day 
transmitted from the shores of England or the United States to an 
Atlantic liner in mid-ocean. 
We may consider in the next place another problem of great prac- 
tical importance, toward the solution of which some considerable 
progress has been made, viz, that of locating the direction of the 
sending station and giving direction to the emitted radiation sent out 
from it. The early attempts to do this depended upon the use of 
parabolic mirrors, or some arrangement of vertical rods equivalent 
to it. But although comparatively short electric waves of a few feet 
in wave length can be directed in this manner in the form of a beam, 
it is out of the question for electric waves hundreds of feet in length, 
because reflection can only take place when the dimensions of the 
mirror are at least comparable with that of the wave length. 
The ordinary vertical antenna, of course, radiates equally in all 
directions, and when it is so far off as to be below the horizon a corre- 
sponding receiving antenna may respond to it, but can not locate the 
position of the sending station. 
It seems to have been noticed by severa: persons that if the antenna 
is not vertical, it radiates rather more in one direction than another, 
and the same for a nonvertical receiving antenna. It is more recep- 
tive to waves coming from one direction than another. Various 
observations on the operation of nonvertical, looped, or duplex 
antenne have from time to time been made by Zenneck, Sigsfe!d, 
Strecker, Slaby, and De Forest, whilst methods for locating the send- 
ing station or directing the transmitted waves were described in 
patent specifications by De Forest, Garcia, and Stone. Although 
claims were made for arrangements said to be effective, these various 
“See The Electrician, Vol. LVIII, p. 710, 1907. 
