v72 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1909. 
into a triangular form, the top ends nearly meeting, the planes of 
these triangles being at right angles to one another, and both of them 
vertical. The nearly closed antenna circuits are then inductively 
coupled with a condenser circuit, which is capable of being swivelled 
around in various directions. If the said condenser circuit is placed 
in such a position as to be coupled with one of the triangular antenne, 
it will cause the maximum radiation to take place in the plane of that 
antenna, but none at all at right angles to it. If it is coupled with 
the other antenna, it will cause radiation to take place to a maximum 
degree in the plane of that second antenna. If, however, the oscil- 
latory circuit is placed in an intermediate position, so as to act 
inductively upon both the nearly closed triangular antenne, then it 
can be shown both mathematically and experimentally that the radia- 
tion of the combined system is a maximum in the direction of the 
plane of the oscillatory circuit which is coupled with the antenna. 
. Hence, with such a combined antenna, we have it in our power to 
: create radiation most strongly in one direc- 
tion, although not entirely suppressed in all 
other directions. By combining together, 
however, a single vertical antenna with two 
nearly closed circuit antenne at right angles 
to one another, Messrs. Bellini and Tosi have 
constructed a complex antenna which has the 
property of producing radiation almost en- 
tirely limited to one-half of the circumja- 
cent space (see fig. 12). It therefore corre- 
sponds to a certain extent in effect to the 
optical apparatus of a light-house, with 
catoptric or dioptric apparatus, which pro- 
jects the light from the lamp largely in one direction. It is not 
yet possible to make with electric radiation of long wave length 
that which corresponds precisely with a beam of hight wholly con- 
centrated along a certain cone or cylinder, but it is possible, by 
the use of a complex antenna as described, to greatly limit the 
diffusion of the radiation. Since radiating and absorbing power 
go hand in hand, it is obvious that such a directive antenna also 
enables the position of a sending station to be located. Messrs. 
Bellini and Tosi have accordingly applied their methods in the con- 
struction of a radiogoniometer and receiving antenna, by means of 
which they can locate the direction of the sending station without 
moving the antenna, but merely by turning around a secondary cir- 
cult into a position in which the maximum sound is heard in a 
telephone connected with the receiver. By the kindness of Captain 
Tosi I am able to exhibit to you their ingenious apparatus (see 
fig. 13, pl. 2): 
Q 
Fie. 12. 
