Nikola Tesla Books
On this occasion I must point out a peculiar feature about the action of the currents developed by this apparatus upon Roentgen tubes. As might be expected, some experiments were carried on in this line also and possibly with greater pleasure than those in other directions, for my conviction is growing stronger every day that, with apparatus such as the present, wonderful results must be secured provided only that a tube is constructed capable of taking up any amount of energy. On my return this task will be a serious one. Many times tubes have been worked here from the secondary but curiously enough, for a reason which is to me not yet clear, they can only work for a few seconds at the most as, almost instantly, they become very highly rarefied and the sparks begin to dart over the glass, the tube becoming useless. No matter how the current was cut down the action took place, unless it was reduced to such an extent that the tube was scarcely excited at all. Already in New York with an apparatus similar to this, though much smaller, I observed that such an action always occurs, in some degree, when the vibrating system possesses a very small resistance and the electrical movement in the circuit connected to the tube is very large. This will be further investigated.
XXXII. This is a central view through the open entrance spoiled ...
Note: Plate XXXIII. is missing. One more photograph is to be made showing a lamp lighted without a coil, merely in series with a plate or object as capacity. If time permits a special coil will be constructed for full power of apparatus and all photographs, as far as practicable, taken outside. Taken in this manner they would be undoubtedly much more interesting to scientific men.
Colorado Springs
Jan. 3, 1900
Photographs taken with Mr. Alley from Dec. 17 to Dec. 31, 1899 and particulars relating to the same.
In the photographs, which will be presently described, 11" x 14" Cramer plates were used, most of which were “instantaneous isochromatic”.
XXXIII. View of the Pike’s Peak Range taken from room through the window glass by moonlight, the night of an eclipse. A gale was blowing and it being impossible to place the camera outside, the photograph was taken in the above manner. As the building was trembling more or less during the sudden gusts of wind the picture is not as perfect as it might have been. The light was magnificent, the moon almost full and a good photograph might have been taken in 10 - 15 minutes. There was, of course, considerable loss in the transmission through the window glass though it was thoroughly cleansed, nevertheless the photograph is as good as if it had been taken in daylight. The exposure was much too long, two hours, from 9 - 11. Had the wind not been blowing a perfect picture would have been obtained in a quarter of that time. The wonderful brightness of the moonlight was increased by the snow which was unusually heavy.
XXXIV. This photograph shows the laboratory viewed from behind with the mountain range from Pike’s Peak to Cheyenne Mountain in the background. There was
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The explanation to Photograph XXII concerning the transmission of power from the excited primary circuit to the “extra coil” via the earth is similar to that he gave in 1893(6). The experiment to which the photograph refers was made with the aim of estimating the power of the oscillator from the thermal effect of the HF current. What Tesla calls the “total energy set in movement” would correspond to the total energy transferred to condenser in the secondary (i.e. the power) if an energy of $!{1 \over 2}$! CV2 is transferred in each half-cycle. It can be shown that the active power dissipated in the circuit is much less than this and is inversely proportional to the Q-factor of the oscillating circuit.
January 2
Tesla gave his observations on 22 pages. On them he described eleven photographs. The explanation along with photograph No. 22 about energy transmission from excitation of the primary circuit to "additional coil" over the earth surface is similar to the one from 1893(6). Otherwise the experiment to which the photograph is related was performed for the purpose of oscillator power estimate on the basis of thermal effects of high frequency current.
That which Tesla calls "total energy placed in motion" would correspond to the total energy which is supplied to a capacitor per second (i.e. power) if energy ½CV2 is supplied during the duration of one half of the period.
It could be shown that the active power which is spent in the circuit is considerably smaller than this power, and opposite, proportionally to the quality factor of the oscillating circuit. On several following photographs, the movable resonant coil with connected bulbs is photographed which is supplied by transmitted high frequency energy. One terminal of this coil is connected to the ground, and the other is open ended or a short piece of wire is connected to it. Bulbs are coupled by means of the auxiliary secondary coil inductively with the secondary coil. The data was not given on the distance of resonant coil from the oscillator coil. Tesla's comment on photograph No. 27 illustrates the interest on the question of electrical lightning, though he worked on this for more than ten years. One earlier discovery on gas elimination and not only filament, when working with high frequency currents is again proven(5).
On photograph No. 28 the bulb is connected in series with a terminal capacitance load. In the calculations "total energy placed in movement" is not taken when it was assumed that the electrostatic energy ½CV2 is spent in the bulb during one half of the period. A similar comment is valid for photograph No. 29.
Tesla mentioned several times that the main transmission from the exciting to the excited circuit is done via the ground. The proof for this statement he found in the experiment illustrated by photograph No. 30. He concluded that the induced voltage in the excited circuit is significantly reduced when the ground connection is disconnected. Photograph No. 31 is an X-ray photograph of a finger. The comments on this experiment are an illustration of Tesla's interest in the radiation field which was mentioned earlier (please see comment on June 6, 1899).
January 3
After description of several photographs showing the laboratory on photograph No. 41, he explains some current streamer transformation. He mentions the current streamer division in the vicinity of the floor, the division and repeated merging of the current streamers, the event of brighter current streamer portions (which he calls sparks), and the distraction of the spark into current streamers and "fire-balls". Particularly interesting are Tesla's observations and comment about the creation of "fire-balls", the event which interested people for a long time. Some data about "ball type" lightning have been found even on Etrurian monuments, in the works of Aristotle, Lucretia and others(63).
Ball-like lightning or "fire-balls", as Tesla calls them, are created during weather disturbances and are considered one kind of electrical discharge. The event in nature is very rare, but nevertheless quite a bit of information has been collected on the basis of which several theories have been established on the cause of this lightning. According to some hypothesis, the "ball-type" lightning is an optical illusion (Tesla thought so as well until he produced ''fire-balls''), according to others this is the track of meteors.
Before Arag's analysis of approximately twenty known events of ball-type lightning in 1838, there was no scientific analysis in the real sense. After publication of Arag's work, ball-type lightning entered in the circle of science problems and they remain to this day a partial puzzle.
Ball-type lightning is a bright sphere, which appears during the storm. In most cases it is red in color, but appears in other colors as well; yellow, green, white and blue. Dimensions are various and the mean diameter is approximately 25 cm. As distinct from usual lightning, ball-type lightning moves slowly, and travels parallel to the ground. They could stop and change their direction of movement, and last even to to five seconds. The characteristics of ball-type lightning changes from case to case, and therefore it is considered that there are various kinds of this type of lightning. According to Singer(63), it is considered today that one theory does not give the explanation for all types of ball lightning in nature.
Despite numerous efforts, only some types of ball-type lightning have been partially produced under laboratory conditions. Amongst those are poorly lit balls created after a strike of usual lightning against some solid matter. Tesla several times mentioned similar events caused by spark strike or current streamer against a wooden object (please see e.g., photograph No. 50). According to new theories, ball-type lightning is in fact the plasma area created in nature by means of electrical discharge. Latest research and calculations by Kapica(64), indicate that the light of ball-type lightning is impossible to explain by means of energy which it could contain at the instant of creation, thus for its maintenance external energy should be supplied. Kapica assumed that the external energy is obtained from naturally created electromagnetic fields. In the beginning a small area of ionized gas, created by previous lightning, or some other electrical event during the storn, is increased on account of the energy of an external electromagnetic field. The diameter of the plasma sphere determines the frequency of the external field, and so the resonance is achieved. The most frequent dimensions of fire-balls require electromagnetic fields of 35 to 100 cm wavelength. According to this theory, it is assumed that some role is played by standing waves created by a reflection of natural electromagnetic waves from the ground. This was partially proven by an experimental method, but there are still problems to which even this theory did not provide satisfactory answers. It has been established that for the maintenance of the plasma chunk in the air, the required electromagnetic field power is approximately 500 watts, which is considerably below the possible power present during an electrical discharge. However, there is very little known about natural electromagnetic waves, and therefore on the basis of this limited data, it is not possible to conclude much.
Tesla's hypothesis of the creation and sustaining of fire-balls contains some assumptions which can be found in the newest theories, but it carries the characteristics of the time in which it was established, so, for example, according to Tesla and Kapica, if the initial energy nucleus of the fire-ball is not sufficient for the ball-type lightning sustenance then it is necessary to supply external energy. Tesla exhausts the energy from other lightning which propagate through the nucleus space of the fireball, and the energy concentration he explains by nucleus resistance, or the higher capability of a rare gas in the nucleus to absorb energy from the other gases which pass through the discharge. In nature there is less likelihood of several lightning strikes passing through the nucleus of a ball-type lightning and therefore the Kapica assumption on the action of other lightning strikes by means of an electromagnetic field and standing waves which they create, is more logical. In Tesla's experiments it is possible that there frequently occurs a ''transfer'' of repeated lightning over the nucleus of ball-type lightning.