Detectives in plain clothes had been following him and watching closely his every move in and out of restaurants and shops and at social affairs; but not the slightest proof could be secured against him.
One noon-time they followed him into a café, where he had gone with a friend. The detectives took seats near him, but each of them sat at different tables in the room full of people.
When in the café the suspect sat next the wall, a habit the detectives had noticed. Consequently, only those persons who sat at one side of him or directly in front could see his face. During the time they were in the restaurant the detectives communicated with each other by tapping on the table tops with a lead-pencil; and something the man said, which the nearest detective heard, led to the climax. One detective rose, paid his check, and loitered near the door; another got up a little later and sauntered out, but returned with a cardboard sign. Going over to the table where the suspected criminal and his friend sat, he deliberately tacked it on the wall above them, then went out again, leaving the third detective to watch the face of the man as he read:
$1000 REWARD
for information leading to the arrest of the murderer of ————————
on March ————, 1876
The man cast a glance about the restaurant, then said to his companion: “Did I show any signs of agitation?” The third detective rose, stepped over to the man, tapped him on the shoulder, and said, “I want you.” There would have been a scene of violence had not the other two detectives closed in on the man, and within six months he paid the penalty of his crime.
If it had not been for the dot-and-dash alphabet, tapped out with lead-pencils, the detectives could not have communicated; but like Edison, they used the means at hand to open up and carry on a silent conversation.
Wireless Telegraphy
Everybody nowadays understands that wireless telegraphy means the transmission of electrical vibrations through the ether and earth without the aid of wires or any visible means of conductivity. The feat of sending an electrical communication over thousands of miles of wire, or through submarine cables, is wonderful enough, for all that custom has made it an every-day miracle. To accomplish this same end by sending our messages through the apparently empty air is indeed awe-inspiring and almost beyond belief. And yet we know that wireless telegraphy is to-day a real scientific fact.
At first sight it would seem that the instruments must be complicated and necessarily beyond the ability of the average boy to make, and far too expensive as well. As a matter of fact, the young electrician may construct his wireless apparatus at a very moderate cost, it being understood that the sending and receiving poles may be mounted on a housetop or barn.
But first let us consider the theory upon which we are to work. There is no doubt but that electricity is the highest known form of vibration—so high, indeed, that as yet man has been unable to invent any instrument to record the number of pulsations per second. This vibration will occur in, and can be sent through, the ordinary form of conductor, such as metals, water, fluids and liquids, wet earth, air and ice. Also through what we call the ether.