Various Tesla book cover images

Nikola Tesla Books

Books written by or about Nikola Tesla

Colorado Springs

Jan. 7, 1900

Photographs taken with Mr. Alley from Dec. 17 to Dec. 31, 1899 and particulars about the same continued:

LVIII. This photograph shows the extra coil in central view with the discharge issuing from two diametrically opposite wires, pointing upwards, which are fastened to the brass ring or last turn on the top. The sparks, passing abundantly to the hood above the coil, produce a most beautiful symmetrical figure, which is rendered still more so by the fine texture and sharpness of the discharge paths. On the top of the coil from the brass ring delicate streamers rise producing the effect of a flame. The two wires from the ends of which the sparks and streamers sally forth glow all along. This is remarkable and indicates the great quantity of electrical movement. The glow of the top turn of the secondary and also that of the wire leading to the extra coil is strong, that of the latter wire being much stronger. Some exceptionally brilliant sparks occur occasionally. This happens when the discharge breaks out on one wire or point much earlier. In this case the spark continues along this path and practically all the energy supplied goes this way. In the experiment, as in most cases before, 100 throws of the switch were made, other particulars remaining unchanged.

LIX. In this plate the extra coil is again shown in central view, only the discharge is made to issue from many wires instead of only from two as before. The wires are fastened to the brass ring and are pointed upward as in the preceding case. This photograph is also symmetrical and extremely beautiful. Some stronger sparks and streamers occurring occasionally present many features of interest. A number of sparks starting from the back avoid the hood, though passing near the same, circle around and finally strike the hood on the front side. One streamer, extremely long, starts upward following the pole for some distance then turns, passing for a good distance horizontally, and finally darts upward through the opening in the roof, evidently carried by a sudden gust of the draught. Several sparks pass closely to the hood upward and return to the same after traversing a considerable distance. All the wires emitting the streamers glow. Again 100 throws of the switch were made and the vibration, as well as other particulars, remained nearly normal.

LX. This is a very interesting plate, the discharge taking place from a ball of 8" diam. and two diametrically opposite wires fastened to the same. The extra coil is again viewed centrally. Very strong sparks pass to the floor, some twisting and darting about curiously and exhibiting several phenomena described already. Sparks and streamers also pass to hood, roof and sides of the building. Some of the streamers attain great length being thirty feet, at least, in a straight line, while some sparks measure twenty feet or more. These latter are very brilliant and fierce. The upper streamers indicate the existence of a strong current of air created by the heat developed by the discharge. Again 100 throws of the switch were made, other particulars remaining the same.

LXI. This is another most beautiful photograph showing streamers and sparks issuing from a disk facing the camera. The extra coil is viewed centrally, as before, the disk forming the free terminal being on a point of the vertical axis of the coil. It seems that in some quick moving streamers the individual discharges are recorded, at least the texture appears far too fine for the break wheel period. Assume, for example, 4000 breaks per




Tesla: “Means for generating electric currents”, U.S. Patent 514 168, Febr. 6, 1894, Appl. Aug. 2, 1893, P-225.

Method of regulating apparatus for producing currents of high frequency”, U.S. Patent 568 178, Sep. 22, 1896. Appl. June 20, 1896, P-228.

Apparatus for producing electric currents of high frequency and potential”, U.S. Patent 568 179, Sep. 22, 1896, Appl. April 22, 1896, P-233.

Method and aparatus for producing currents of high frequency”, U.S. Patent 568 179, Sep. 22, 1896, Appl. July 6, 1896, P-237.

Apparatus for producing electrical currents of high frequency", U.S. Patent, 568 180, Sep. 22, 1896, Appl. July 9, 1896, P-241.

Apparatus for producing electric currents of high frequency", U.S. Patent, 577 670, Feb. 23, 1897, Appl. Sep. 3, 1896, P-245.

Apparatus for producing currents of high frequency", U.S. Patent, 583 953, June 8, 1897, Appl. Oct. 19, 1896, P-249.

January 7

This is the last entry in the diary. Apart from the usual description of photographs, Tesla writes about experiments he intends to carry out on his return (where?). He qualifies the experiments to date as satisfactory, considering that his aim was “to perfect the apparatus and make general observations”. The apparatus which he was then envisaging for future experiments was to be an improved oscillator which would enable better results than any he had so far obtained.

January 7

Last day, along with the usual descriptions of photographs, he talks about future experiments after returning (where?).

About experiments performed until then, he says they were satisfactory based on the fact that his goal was the "apparatus improvement and the achievement of a general picture". Future apparatus about this he now thinks, will be an improved oscillator and it will enable the achievement of results better than all those until then. It is known that immediately after returning to New York (and according to news media he arrived in Feb., 1900), Tesla started to materialize the idea on "world radio station" and its construction started in 1901 on Long Island in the vicinity of New York. Tesla lacked the financial means, and the help of Morgan and others was not sufficient, and therefore Tesla was forced to discontinue the construction of such a station in 1905.


Lowercase tau - an irrational constant defined as the ratio of the circumference of a circle to its radius, equal to the radian measure of a full turn; approximately 6.283185307 (equal to 2π, or twice the value of π).
A natural rubber material obtained from Palaquium trees, native to South-east Asia. Gutta-percha made possible practical submarine telegraph cables because it was both waterproof and resistant to seawater as well as being thermoplastic. Gutta-percha's use as an electrical insulator was first suggested by Michael Faraday.
The Habirshaw Electric Cable Company, founded in 1886 by William M. Habirshaw in New York City, New York.
The Brown & Sharpe (B & S) Gauge, also known as the American Wire Gauge (AWG), is the American standard for making/ordering metal sheet and wire sizes.
A traditional general-purpose dry cell battery. Invented by the French engineer Georges Leclanché in 1866.
Refers to Manitou Springs, a small town just six miles west of Colorado Springs, and during Tesla's time there, producer of world-renown bottled water from its natural springs.
A French mineral water bottler.
Lowercase delta letter - used to denote: A change in the value of a variable in calculus. A functional derivative in functional calculus. An auxiliary function in calculus, used to rigorously define the limit or continuity of a given function.
America's oldest existing independent manufacturer of wire and cable, founded in 1878.
Lowercase lambda letter which, in physics and engineering, normally represents wavelength.
The lowercase omega letter, which represents angular velocity in physics.