892 
rents of electricity are transmitted in the 
first circuit so as to form signals, letters 
and words in Morse character. The ef- 
fects of the rise and fall of those cur- 
rents are transmitted as electro-magnetic 
waves through the intervening space, and 
if the secondary circuit is so situated as 
to be washed by these etheral waves, their 
energy is transformed into secondary cur- 
rents in the second circuit, which can be 
made to affect a telephone and thus to 
reproduce the signals. Of course, their 
intensity is much reduced but still their 
presence has been detected, though five 
miles of clear space have separated the 
two circuits. 
Such efforts have been known scientifi- 
cally in the laboratory since the days of 
Faraday and of Henry, but it is only within 
the last few years that I have been able to 
utilize them practically through considera- 
ble distances. This has been rendered pos- 
sible through the introduction of the tele- 
phone. 
Last year (August, 1896) an effort was 
made to establish communication with the 
North Sandhead (Goodwin) lightship. The 
apparatus used was designed and manufac- 
tured by Messrs. Evershed and Vignoles, 
and a most ingenious relay to establish a 
call was invented by Mr. Evershed. One 
extremity of the cable was coiled in a ring 
on the bottom of the sea, embracing the 
whole area over which the lightship swept 
while swinging to the tide, and the other end 
was connected with the shore. The ship 
was surrounded above the water line with 
another coil. The two coils were separated 
by a mean distance of about 200 fathoms, 
but communication was found to be im- 
practicable. The screening effect of the 
sea water and the effect of the iron hull of 
the ship absorbed practically all the energy 
of the currents in the coiled cable, and the 
effects on board, though perceptible, were 
very trifling—too minute for signalling. 
SCIENCE. 
[N.S. Vou. VI. No. 155. 
Previous experiments had failed to show 
the extremely rapid rate at which energy is 
absorbed with the depth or thickness of sea 
water. The energy is absorbed in forming 
eddy currents. There is no difficulty what- 
ever in signalling through 15 fathoms. 
Speech by telephone has been maintained 
through 6 fathoms. Although this experi- 
ment has failed through water, it is thor- 
oughly practicable through air to consider- 
able distances where it is possible to erect 
wires of similar length to the distance to be 
crossed on each side of the channel. It is 
not always possible, however, to do this, 
nor to get the requisite height to secure the 
best effect. It is impossible on a lightship 
and on rock lighthouses. There are many 
small islands—Sark, for example—where it 
cannot be done. 
In July last Mr. Marconi brought to 
England a new plan. My plan is based 
entirely on utilizing electro-magnetic waves 
of very low frequency. It depends essen- 
tially on the rise and fall of ewrrents in the 
primary wire. Mr. Marconi utilizes elec- 
tric or Hertzian waves of very high fre- 
quency, and they depend upon the rise and 
fall of electric force in a sphere or spheres. 
He has invented a new relay which, for 
sensitiveness and delicacy, exceeds all 
known electrical apparatus. 
The peculiarity of Mr. Marconi’s system 
is that, apart from the ordinary connecting 
wires of the apparatus, conductors of very 
moderate length only are needed, and even 
these can be dispensed with if reflectors 
are used. 
The Transmitter.—His transmitter is Pro- 
fessor Righi’s form of Hertz’s radiator 
(Fig. 2). 
Two spheres of solid brass, 4 inches in 
diameter (A and B), are fixed in an oil- 
tight case D of insulating material, so that 
a hemisphere of each is exposed, the other 
hemisphere being immersed in a bath of 
vaseline oil. The use. of oil has several 
