A RETROSPECT OF WIRELESS COMMUNICATION. 557 
The only method of detecting them at first was the scintillee which they produced. 
I found another means of detecting them by two knobs in loose contact in the circuit 
of a battery and galvanometer, or again in any form of loose joint and a telephone. 
This was the coherer principle, subsequently made more practicable by Branly in 
France, who found that the resistance of the metal coating smeared on paper, or a 
tube of iron filings, fell suddenly when a spark was taken in its neighbourhood. 
Now the era of scientific discovery was nearly complete. The rest was what 
happens when any application is made of science on an extensive scale. A multitude 
of ingenious inventors combined their ingenuity and experience to apply the process 
on an engineering scale and to improve it out of all recognition. In 1894 I showed 
that Hertz’s waves, combined with a Branly detector, could be used for sending and 
receiving messages in the Morse code by the emission and detection of waves from 
an electric oscillator, a signal or series of waves being emitted and detected at every 
spark. 
- About the same time, or soon after, Prof. Righi took the matter up and, in Italy, 
Senatore Marconi began applying the same process privately in his father’s garden. 
In 1896 he came over to this country with an introduction to Sir William Preece, 
chief engineer to the Post Office, aroused his interest and enthusiasm for this method 
of signalling, and secured his co-operation. No doubt he encountered many diffi- 
culties, not only scientific and engineering but also financial; but he persevered and 
won through, and to him must be attributed the great success of wireless telegraphy. 
Before his patent was published, I perceived that something more would be wanted ; 
that as stations multiplied there would have to be selection, and that tuning was 
necessary, not only to give selection, but also to give-sufficient sensitiveness. One 
station could be worked upon its own wave length, by a receiver with capacity and 
self-induction attuned to that rate of vibration. Such a receiver would be very 
sensitive to one length of wave, and would exclude all other waves. This was patented 
in 1897, and was regarded afterwards by the Courts as the bottom patent for Tuning ; 
it was extended by Lord Parker for a total period of 21 years, and for the last seven 
years was purchased by the Marconi Company. Other improvements were made, 
too numerous to go into. Mazrconi’s special kind of radiator was an elevated aerial 
connected through a spark gap to the earth. He was thus able to reach great distances, 
because the waves oscillated in a vertical plane, so that the electrical vibrations were 
not wiped out, as they might have been if they had been horizontal, by the resistance 
of the earth and the sea-water over which they went. 
Then came another striking discovery, which must be credited to Mr. Marconi 
working with unexampled energy on an extensive scale. He arranged for a large 
sending station in Cornwail, and travelled across to America to see if he could hear 
the signals in Newfoundland. I imagine that the scientific world must have been 
against him in this enterprise, since the waves could not penetrate the substance of 
the earth, and could not apparently travel round it to reach America. They would 
apparently travel in straight lines. But enterprise was rewarded, and the signals 
were heard: only three dots signifying the letter S$; that was the arranged thing to 
be sent. It was enough: it began the series of Transatlantic communication. There 
was something in the earth’s atmosphere, an upper layer postulated by Heaviside, as 
an effect due to the solar radiation in ionising the upper air, which caused the upper 
air to act as a kind of mirror, and make the whole earth into a whispering-gallery, 
so that waves impinging on the layer no longer went straight, but curved round until 
they reached the Antipodes ; so that waves sent out in this country could be heard 
ultimately all over the surface of the earth. When I say ‘heard,’ the waves could 
not be heard; they make no impression on our senses until they are received by a 
suitable and attuned apparatus, when the high frequency electrical disturbance is 
transmuted into the low frequency mechanical disturbance that we call sound. No 
sound travels from the distant station to the receiver, nothing but ether waves which 
travel with the velocity of light ; so that they reach the whole earth simultaneously. 
But at the receiving station they are converted into sound energy, and then operate 
on a telephone. 
So far all signalling had been of a spasmodic or discontinuous character. A short 
series of waves was emitted by each spark, and it was by a succession of sparks that 
messages were sent. There was no continuity in the waves themselves. But many 
people perceived that it would be an improvement if, instead of generating a jerky 
series of independent trains of waves, we could generate a continuous wave at the 
