58 Dr. Howard on Electric Radiation. 



Nothing approaching continuous radiation can be main- 

 tained at this enormous intensity without the expenditure of 

 great power, a hundred and thirty horse-power if my calcula- 

 tion is right. Under ordinary circumstances of excitation 

 the intervals of darkness are enormous ; if they could he 

 dispensed with, some singular effects must occur. To try 

 and make the radiation more continuous a large induction-coil 

 excited by an alternating machine of very high frequency, 

 or by a shrill spring- break, might be tried. But even if 

 sparks were made to succeed one another at the rate of 1000 

 per second, the effect of each would have died out long before 

 the next one came. It would be something like plucking a 

 wooden spring which, after making 3 or 4 vibrations, should 

 come to rest in about two seconds, and repeating the operation 

 of plucking regularly once every two days. 



Statement of Results hy Dr. Howabd. 



The apparatus used consisted of (1) an oscillator, or trans- 

 mitter, with exciting coil ; (2) a resonator or receiver, and 

 (3) two lenses of pitch. We shall describe these in order. 



The Oscillator or Source of Radiation. — This was made in 

 two similar halves, each constructed by soldering to one end 

 of a brass rod, 6 centim. long and *95 centim. diameter, a thin 

 circular copper disk of 4 centim. radius. To the other end 

 was soldered a spherical brass knob of 1 centim. radius, 

 highly polished. A small hole was drilled in each rod at a 

 distance of 1*3 centim. from the knob to allow of the insertion 

 of connecting wires to the RuhmkorfT coil by which it was 

 excited. The two disks were cemented to two small wooden 

 blocks which could be clamped in any position on a vertical 

 glass rod. By this means the distance between the knobs 

 could be easily adjusted, and the apparatus could be inclined 

 when wished. 



The induction-coil was of the usual pattern with hammer- 

 break. With the current used (supplied by 6 accumulator- 

 cells) it gave a continuous stream of sparks between two 

 points 2*5 centim. apart connected to the secondary terminals. 

 The knobs of the oscillator were usually separated by a space 

 of from *7 to 1/0 centim. They required cleaning about every 

 20 minutes owing to burning produced by the spark. This 

 burning was always greater at one knob than the other ; 

 greatest apparently at the one that mattered least, for if the 

 primary current was reversed after the oscillator had been 

 working some time the intensity of its radiations immediately 

 decreased perceptibly. 



The length of a complete wave emitted by the oscillator, 



