Nikola Tesla Books
Books written by or about Nikola Tesla
a rarefied gas a discharge of sufficient intensity, preferably one of high frequency, the resistance of the gas may be so diminished that it falls far below that of the best conductors. So through just a bulb of highly rarefied gas an immense amount of energy may be passed and currents of a maximum strength such that they can not traverse a copper wire, owing to its resistance and impedance, may be made to traverse the rarefied gas. The plan now is to constitute a circuit composed of a rarefied gas column, heated by auxiliary means to a very high incandescence so as to offer an inconceivably small resistance to the passage of the current and use this column for the purpose to which it is suited.
To illustrate the use of this idea in telegraphy, for instance the diagram below is shown in which S is a source of oscillating currents of preferably high frequency, C a condenser in shunt to same, L a coiled glass tube containing the rarefied gas which is kept at a high degree of excitation. The conductor L is connected, as in my system, to earth and a capacity preferably elevated. Through this path the currents of a distant transmitter are made to pass which are of the same frequency and cause a great rise of the e.m.f. on the terminals of conductor L, which may then be utilised to affect a receiving instrument in many ways
(To follow up).
Colorado Springs
June 25, 1899
The following plan seems to be well adapted for magnifying minute variations such as are produced by the action of a microphone, for example. Suppose that on a rotating or, generally speaking, moving surface of iron (polished or smooth) there is arranged a brush of soft iron, steel or at least having a surface of such magnetic materials whatever they be then there will be a certain amount of friction developed on the contact surfaces between the brush and moving surface and the brush will be dragged in the direction of movement of the surface.
A spring may be used to pull the brush back against the friction and to maintain it in a position of delicate equilibrium. Let now the brush or surface be but slightly magnetized, then the friction between the magnetic surfaces will be enormously increased and the brush will be pulled forward with great force. A small variation in the magnetization of the surface will thus make great changes in the force exerted upon the brush, and the movements of the latter may be utilised for any purpose, as for instance in loud speaking telephones, or in perfecting a “wireless telephone” or such purposes. A simple form of apparatus is illustrated below: A is a rapidly rotating
46
June 24
Rarefied gases had long interested Tesla, and his work on their conducting properties, especially at high frequencies, is well known, e.g. the patents on an electric lighting system and an incandescent lamp(37). He presented detailed analyses of the same problems in his famous lectures(4, 5, 6). Rarefied gas as a conductor is also referred to in his patent application “System of transmission of electrical energy”(13).
June 24
Tesla was for many years, interested in rare gases and his works on current flow (particularly high frequency current) through gases are known. From this field are the patents on electrical lighting system and lamps with red hot electrodes in the vacuum(37). Tesla analyzed the same problems in detail and presented them in his famous lectures about which there was a mention(4,5,6). The rare gas as conductor is mentioned in the patent "Electrical Energy Transmission System"(13) as well. Now Tesla mentions the possibility of the use of gas in a tube instead of metal conductor. Gas is heated to red hot state from an auxiliary source, by which its resistance is reduced below the one the metal would have. So the coil with high quality factor suitable for receiver circuit was obtained. The system obviously is not practical, but Tesla considers that the idea has to be developed on the potential possibility for the purpose of selectivity and sensitivity improvement of weak signals receiver.
June 25
The device shown in the drawing was intended to amplify the vibrations, in the following way: some of the power driving cylinder A is converted by friction of brush b against A into vibrations of b. Since the friction is a function of the current in the electromagnet, the vibrations of b have a time variation similar to the time variations of the current. If the circuit of the electromagnet includes a microphone and a battery, then the device should amplify the speech signal, brush b vibrating in synchronization with the speech pressure but with much more energy. This amplified signal could be used in a modulator (see June 13th and 14th). The drawing shown on p. 405 (from Tesla's slide in Nikola Tesla Museum, Belgrade) illustrates how Tesla thought of implementing some of these ideas*.
June 25
The device which is now shown on the drawing is intended for the vibrations amplification so that power portion required for the wheel 'A' rotating by means of electromagnet and track 'b' friction against wheel 'A' converts into track 'b' vibrations. Because the friction is dependent on current through electromagnet, longitudinal movements of track 'b' are proportional to current changes through the electromagnet.
Providing the microphone and battery are in the electromagnet circuit, the voice can be amplified by means of this device and track 'b' will vibrate in rhythm with the sound pressure, but with considerably higher intensity. So amplified vibrations can be used in a modulator assembly (please see June 13 and 14). According to drawing shown on page 17 (Tesla's slide from archives in Nikola Tesla Museum in Belgrade) it is seen how Tesla imagined that some of his ideas could be materialized.**
** So far it hasn't been established whether Tesla patented or he attempted to patent this modulator. It appears the the slide represents the copy of a drawing which was being prepared for patent submission.
