The Last of Tesla's Tower

The mysterious steel tower built by Nikola Tesla at Shoreham, L. I., about twenty years ago, in connection with some of his experiments, was demolished by order of the Government recently. The tower was described not long ago in these columns at the time when rumor pointed to the resumption of experimental work there. This rumor proved unfounded, and since the entrance of the United States into the war it has been suspected that the tower was being used for wireless purposes by German spies. Strangers are said to have been seen about the place during the past month. Tesla erected the tower, which was about 185 feet high, with a well 100 feet deep, for use in experimenting with the transmission of electrical energy for power and lighting purposes by wireless. The equipment cost. nearly $200,000. Says a writer in The Electrical Experimenter (New York, September):

"The late J. P. Morgan backed Nikola Tesla with the money to build this remarkable steel tower, that he might experiment in wireless even before people knew of Marconi.

"Briefly explained, the Tesla theory is that a wireless tower, such as that here illustrated and specially constructed, to have a high capacity, acts as a huge electric condenser. This is charged by a suitable high-frequency, high-voltage apparatus, and a current is discharged into the earth periodically and in the form of a high-frequency alternating wave. The electric wave is then supposed to travel through the earth along its surface shell, and in turn to manifest its presence at any point where there might be erected a similar high-capacity tower to that above described.

"A simple analogy to this action is the following: Take a hollow spherical chamber filled with a liquid, such as water; and then, at two diametrically opposite points, let us place, respectively, a small piston pump, such as a bicycle pump, and an indicator, such as à pressure gage. Now, if we suck some of the water into the pump and force it back into the ball by pushing on the piston handle, this change in pressure will bo indicated on the gage secured to the opposite side of the sphere. In this way the Tesla earth-currents are supposed to act.

"The patents of Dr. Tesla are basically quite different from those of Marconi and others in the wireless-telegraphic field. In the nature of things this would be expected to be the case, as Tesla believes, and he has designed apparatus intended for the transmission of large amounts of electrical energy, while the energy received in the transmission of intelligence wirelessly amounts to but a few millionths of an ampere in most cases by the time the current so transmitted has been picked up a thousand miles away. In the Hertzian-wave system, as it has been explained and believed in, the energy is transmitted with a very large loss to the receptor by electromagnetic waves which pass out laterally from the transmitting-wire into space. In Tesla's system the energy radiated is not used, but the current is led to earth and to an elevated terminal, while the energy is transmitted by a process of conduction. That is, the earth receives a large number of powerful high-frequency electric shocks every second, and these act the same as the pump piston in the analogy.

"Quoting from one of Tesla's early patents on this point: 'It is to be noted that the phenomenon here involved in the transmission of electrical energy is one of true conduction and is not to be confounded with the phenomena of electrical radiation, which have heretofore been observed, and which, from the very nature and mode of propagation, would render practically impossible the transmission of any appreciable amount of energy to such distances as are of practical importance.'"