Wireless Telegraphy. 303 
contact between the plugs allowed the current from the battery to flow round 
the circuit and close the relay, which in turn actuated the telegraph receiver. 
When the oscillations ceased, the circuit was broken by means of an instrument 
known a8 a tapper. This was very similar to an ordinary electric bell, but the 
hammer instead of striking a bell struck the coherer and so caused the filings 
to fall into their normal position and cease making contact with the plugs. 
For transmitting, Marconi at first used the oscillator designed by Righi, but 
found that by raising one of the capacity plates of this, and one of the plates 
of his receiving circuit, to a height, he could receive messages at a greater dis- 
tance. Later he discarded these plates, substituting for them the antenna 
or aerial wires, which are now usually placed at a height varying from 150 
to 250 feet above the ground, The other capacity area, at both the sending and 
receiving stations, he also did away with, utilizing the earth itself in its place. 
There were several reasons for heightening the upper capacity or aerial, one 
of them being in order to avoid screening of the waves by buidings, etc., the 
others of a technical nature too deep to go into here. 
Tn the Lodge-Muirhead system, the lower capacity is still used, in the shape 
of a second antenna placed below the first, a short distance above the ground. 
The advantage claimed for this is that the instruments are not so liable to be 
affected by atmospheric disturbances as when connected to the earth. 
Marconi succeeded in establishing communication across the English Channel 
in March, 1899. By 1901 several ships had been fitted and were working 
successfully at distances ranging up to about 100 miles. About this time 
several other systems came into prominence, notably the Lodge-Muirhead, De 
Forrest, Fessenden, and the Telefunken, but to go into details regarding each 
System is out of the question. Each has its particular advantages and each 
seems to have its particular disadvantages. 
In 1902 Marconi brought out a new form of receiver known as the magnetic 
detector. This instrument depends upon the property of “ hysteresis ’’ in 
iron for its action ; and has proved a far more reliable and delicate instrument 
than the coherer. It increased the distance over which it was possible to 
receive messages enormously, and, by the end of 1903, it was found possible, 
by means of a 40 H.P. station in Cornwall and a similar one at Cape Cod, to 
keep always in communication with vessels crossing between England and the 
United States ; and early the following year a daily newspaper service was 
inaugurated on some of the more important liners on this route. 
Th the same year Marconi succeeded in sending a message right across the 
Atlantic but owing to the various difficulties it was not until four years later 
that so great a distance became really practicable. On October 17th, 1907, how- 
ever by means of a 500 .P. station near Slyne Head in Ireland, and anotlier 
at Sydney, Cape Breton, a commercial transatlantic service was inaugurated, 
and it then fell to my lot to receive the first message from Cape Breton—the 
second message ever sent right across the Atlantic. 
