THE CATHODE RAY OSCILLOGRAPH 



11 



is largely abandoned in these tubes, and metal is substituted. The 

 applied voltage is very high, of the order of 50,000 volts. This makes 

 a rather formidable piece of apparatus (Fig. 15), but quite a useful one. 

 In the last few >ears several different tubes of this type have been 

 developed. Aside from Dufour's tube, there are those of Rogowski 

 in Germany, Wood in England, Berger in Switzerland, Norinder in 

 Sweden, The Westinghouse Co. and the General Electric Co. in this 



Fig. 16— Wood, 1923.15 



country (Figs. 16-18, 21). All of them involve complicated tubes and 

 control circuits. Some tubes are made to operate during a single peak 

 of a 60 cycle wave. With others there are ingenious switching devices 

 that start the tube operating at the very beginning of the electrical 

 impulse to be studied, and the tube then proceeds to record the rest 

 of the impulse. When we consider that the impulse may be a stroke 

 of lightning on a transmission line, we realize that there are some 

 things that are "faster than greased lightning." 

 " Wood, A. B., Phys. Soc. Land. Proc, 35-2, p. 109, 1923. 



