ELECTRIC WAVE TELEGRAPH Y—FLEMING. 191 
sending station is easily located. It will be seen, therefore, that two 
well-defined principles had been arrived at by Marconi. First, that 
the nonsymmetry of the radiation and reception depends upon the em- 
ployment of antennz having their horizontal portions large compared 
with the vertical, and secondly, that the maximum radiation is in the 
direction opposite to that in which the free end of the horizontal part 
points. These observed effects rest on a sound scientific basis, and, as 
T have shown, are immediately derivable from first principles. 
Previously to Marconi’s experiments no definite guiding principles 
as to directive telegraphy had been published, but a number of uncon- 
nected observations made, not always correctly interpreted or even 
described, and in any case with limited application. 
Meanwhile, however, Prof. F. Braun, of Strassburg, had been 
engaged on a different plan for directing the radiation from antenna. 
Briefly stated, his method is as follows: He erects three vertical 
antennee at the corners of an equi- 
lateral triangle, or four at the cor- 
ners of a square, the sides of which : eS 
are about equal to the height of the 
antenne, and he creates in them 
electrical oscillations which have a 8 
defined and constant difference of 
phase by methods contrived by 
him, Doctors Papalini and Man- 
delstam, not yet fully described. 
It is found that the waves sent off 
from these three antenne interfere 
with each other in an optical sense, 
exalting each other in some direc- 
tions and nullifying each other in 
other directions, in accordance with their relative amplitude and phase 
difference. The resultant effect can be so arranged that the radiation 
is extremely unsymmetrical, being much- more toward one side than 
the other. The intensity in various azimuths may be represented by 
the radi vectores of a sort of oval or heart-shaped curve, the triple 
transmitter occupying a position on the cusp or apex of the curve. 
(See fig. 22.) It will be seen, therefore, that popular notions on the 
' subject of directive telegraphy are wide of the mark. Whilst we can 
not yet project a narrow beam of long-wave electric radiation in any 
required direction, or focus it entirely on a given receiving station at 
a great distance, much can be done to prevent radiation being sent out 
from transmitters in directions in which it is of no use or not desired. 
At coast stations communicating with ships at sea something has 
already been done to achieve this result. Mr. Marconi has for some 
Fic. 21.—Marconi localizing antenna. 
