Currenh by means of the " Pliaseograph."' 



975 



There remains to be described the mounting and the special 



arrangements, as shown by fig. 6. 



The Nernst-style A throws a sharp 

 light on a small diaphragm, which at 

 exposure can be shut with a shutter. By 

 the aid o£ the two lenses, L x and L 2 , an 

 image is formed on the ground glass- 

 plate EF. For photographic purposes 

 the latter can be replaced by a chassis 

 with plate. The lens and the diaphragm 

 are sheltered from outside light by a 

 cardboard tube. 



If we want to study a current curve, 

 i. e. use the phaseograph as an ordinary 

 single oscillograph a revolving mirror 

 with driver is put on, and the ground 

 glass-plate is removed. The image then 

 appears on the screen BC; the desired 

 current curve is obtained by putting 

 the mirror in rotation. 



By means of binding- screws and 

 interrupters (S 12 s) on the outside of the 

 box the electric current is conducted to 



the electromagnet (Si) and the two measuring-wires (S 2 S 3 ) 



IV. Other double Oscillographs. 



In this place it may be convenient to mention some other 

 oscillographs with two co-operating systems, which were 

 constructed about the same time as the one I have just 

 described. 



According to a communication in Verhandl. der deutsch. 

 Phys. Gesellsch. xi. (1909), A. Wehnelt has made use of 

 two oscillograph-slides, one of wdiieh was introduced into a 

 magnetic field, which was to be examined for the demon- 

 stration of magnetization curves. At the request of Siemens 

 and Halske, Berlin, Hansrath tried to use this principle 

 for registering hysteresis curves. The method in this form, 

 however, proved useless, and the instrument brought into the 

 market was composed of an " abstimmbar " vibration galva- 

 nometer on an ordinary oscillograph-slide. 



The '* Hysteresigraph" constructed byH. Abraham served 

 the same purpose. 



F. Piola's double oscillograph may also be mentioned. It 

 consists of two turning-coils at right angles. Its use is con- 

 fined to slowly variable fields. . . 



