Despite this article's claim that this demonstration employed Clarke's "recently invented system of wireless telegraphy", the apparatus used actually was identical to what Oliver Lodge had employed in similar demonstrations beginning in 1894. Also, write-ups of these sort did not always make clear that the radio waves were not directly blowing up ships or ringing bells, but merely were being used to activate, at a distance, devices which had been placed in the objects used in the demonstration.
New York Times, May 7, 1898, page 12:
NEW WAY TO FIRE MINES
A Successful Exhibition of Electrical Transmission Without Wires in the Garden.
MINIATURE SHIP BLOWN UP
At the Show in Madison Square Garden a Telegraph Instrument Is Made to Ring Out Signals by the Same Method.
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W. J. Clarke, general manager of the United States Electrical Supply Company, gave the first public exhibition of his recently invented system of wireless telegraphy at Madison Square Garden yesterday afternoon. By touching an instrument placed in the southern gallery a miniature Spanish cruiser anchored in the fountain lake on the lower floor, 90 feet away, was blown into the air, together with a considerable quantity of water, which fell on those who were not quick enough in getting out of the way.
The first movement of the machine and the explosion were simultaneous. There was no connection between the transmitter and the vessel in the lake. But a coherer was placed at the edge of the lake, connected with a short wire which runs upward. A bell stationed across the Garden in the northern gallery, 180 feet from the transmitter, was made to ring in the same way that the explosion was caused.
The transmitter cannot be briefly described so as to be understood by one unacquainted with electrical contrivances. What it does is to create electrical sparks, which pass between metallic balls and produce violent electrical oscillations, which in turn generate electric waves which go out into space in the form of ever-increasing spheres. These spheres have the power of passing through any material, the walls of a building, or a crowd of people presenting no appreciable impediment to the passage of the waves.
The most essential part of the receiver in the northern gallery, where the bell is placed, is the coherer, which is thus explained by Prof. Clark:
"This little coherer is a most interesting piece of apparatus, and consists of a glass tube, in which are fitted two sliding plugs of metal, so arranged that the distance between them in the centre of the tube is adjustable, the space between the plugs being filled in with a prepared metallic powder. This powder, when lying in its normal condition, presents a very high resistance to the passage of the electrical current, often amounting to 20,000 ohms, an ohm being the unit of electrical resistance. When the electric waves from the transmitter strike this little coherer its resistance instantly decreases, often reaching as low a point as six or seven ohms. This enormous decrease in resistance allows the current from the single cell of the dry battery to pass through the magnet coils of a telegraph relay, which is placed in circuit with the coherer. The relay magnets by their magnetism then pull up the armature, and this armature in its turn makes an electric contact, which closes the local circuit of the apparatus and clicks an ordinary telegraph sounder, rings a large vibrating bell, fires a cannon or mine, starts or stops a steam engine, or, in fact, can be made to accomplish anything that we wish in this direction."
Mr. Clarke's exhibit is so perfectly adjusted that a large six-inch vibrating bell placed in the case containing the receiver is continually ringing out the Morse signals "N. Y.," "N. Y.," "N. Y.," and attracting universal attention by its wonderful performance. There is no connection whatever between the transmitter and the receiver; in fact, the electrical waves do not seem to be interrupted in the least by the iron pipes which are used for the fountain in the centre of the Garden or by the large crowds of people which continually surround the apparatus.
These exhibitions are given four times each day at the electrical show. One day next week an exhibition will be given by which a transmitter placed on the roof of Madison Square Garden is to blow up a vessel five miles away in New Jersey.
By the use of several instruments, Mr. Clarke says, he is now prepared to send messages between New York and Chicago.