By A Hobiest
Like most of the human race, I have hobbies, and one of them is photography. In this most interesting pursuit I delight in attempting unusual subjects, overlooked by the eagle eye (or less) of my fellows. I suppose that the reader gathers from this that I dabble in the outskirts and leave the more serious phases for those better qualified to handle them, and this I will not dispute, at the same time I find much of beauty in some of the unexplored corners.
Fig. 1. Discharge of 1,000,000 volt transformer. flame 10 feet long. - By Percival E. Fansler.
In my profession as an electrical engineer, I have often marvelled at the strange outbreaks of this wonderful form of energy and have often wished that it were possible to record on a photographic plate, the brilliant manifestations of power accompanying high potential discharges. Recently, taking advantage of an exceptional opportunity, 1 made careful photographic study of phenomena produced by
Fig. 2. Discharge of 50-inch Induction Coil. Sparks 48 inches long. - By Percival E. Fansler.
appartus second to none in the world, and the pictures accompanying this article are typical, representing several distinct types of discharges. Before taking up the pictures in detail I might say that an electrical discharge results when two bodies, at a difference of potential or at a difference of electrical pressure, are separated by a medium, the dielectric strength of which is too low to withstand the strain imposed upon it. In other words, if we have a water pipe, closed at the end with a wooden plug, and if the pressure of the water is increased, a point is reached where the plug is forced from its seat, and the pressure is released.
This is precisely what happens when the secondary terminals of a transformer are brought into too close proximity; the difference of electric pressure existing between them is so great that the air gives way and we have an electric discharge or spark, the character of which varies with the conditions. An appreciation of the figures to be given may be gained from the statement that 'the pressure between the wires of an ordinary electric light circuit is 110 volts, and that it takes about 25.000 volts to jump an air gap of 1 inch. Fig. 1 is the discharge of a 1,000,000
Fig. 3. Flaming Discharge of 250,000 volt Trans-former.-By Percival E. Fansler.
volt transformer, the highest pressure transformer, by three-fold, ever built. It was designed by the electricial engineering department of Purdue University, and will be used in research work. Over 100 h. p. was required to create the discharge shown, for which the terminals were separated five feet.
The photograph was made in the open air and the wind blew the flame out to the length of nearly ten feet. The terminals consisted of two brass rods held vertically on long glass arms, the lower ends 6 feet apart, the under about 6. On closing the switch a brilliant discharge occurred between lower ends of the rods, disappearing instantly, to be followed by others at intervals or 1-120 second, each a little higher than the preceding, owing to the fact that the heated path had a tendency to rise. This accounts for the ribbon effect, each individual discharge with its accompanying heat band being clearly defined. The exact exposure may be calculated by counting the number of discharges and figuring 120 to the second; in fact, this is an excellent although impracticable way of calibrating shutters.
Fig. 2 is from a similar but smaller transformer of the same type, operating in still air, and producing a more unbroken impression.
Fig. 4. Spark Gap of De Forest Wireless Transmitting Station. - By Percival E. Fansler.
Fig. 3 is the discharge of the largest induction coil in the world, one capable of giving a spark 60 in. long, or 18 in. longer than the classic Spottswoodie coil. This spark differs from the first two in that it is of a much higher frequency; that is, as many as 2000 distinct discharges may occur in a second.
The last picture, Fig. 4, is the spark produced in a DeForest wireless telegraph station, and was taken when messages were being transmitted from St. Louis to Chieago, a distance of 460 miles.
The discharge, unlike the others, was through but a short distance the terminals of the 60,000 volt transformer being separated but an inch, yet 20 h. p. was dissipated in the rupture and the copper flanges and air blast shown indicate the amount of heat generated and dissipated. This is, to me, a wonderful picture, lacking, it must be admitted, in composition, and with other faults, and yet it vividly portrays the utilization of a vast amount of energy for the needs of man, aud in a most fascinating and spectacular way.-" Photographic Times."