Tesla Transformers for Roentgen Photography

Fig. 1 shows a complete Tesla apparatus, being patented by Mr. L. Miller, for obtaining high tension oscillating discharges from the street electric light mains, where the current is alternating. The illustration is taken from a set of apparatus supplied to St. Bartholo- mew's Hospital for obtaining photographs of injured limbs, &c., by means of Röntgen rays. Messrs. Miller & Woods supply a standard set which gives a stream of sparks over more than a 6-inch air gap. The set consists of a step up transformer (fig. 1) from 100 volts to about 6,000 volts, and taking the same current as two lamps of 16 candle-power each; a condenser; and a Tesla transformer to about 70,000 volts.

The condenser discharges by rapid oscillations of current across the spark gap (shown in figure) through the primary thick wire winding of the Tesla coil. Induced currents are then set up in the inner thin wire secondary winding of the Tesla coil. These are led to the discharge rods and can be used to excite Röntgen rays in a single or double focus tube as shown, or demonstrate the Tesla experiments. The boxes in which the above are contained are filled with mineral oil. Fig. 2 shows a high tension transformer which can be used up to about 4,000 volts without oil. It is said to be a neat compact form of transformer for exciting vacuum tubes, ozone generators, &c., and can readily be connected to the electric mains by means of a lampholder attached to a piece of flexible cord.