4' - Art. 7.— K. Yainada: 



iron and nickel spectra can be taken on the same plate. More- 

 over, I soldered a piece of the above mentioned nickel-steel, 

 about 10 mm in length and 2 mm in diameter, to a brass rod. 

 When strong fields were required, the proximity of the magnet 

 poles necessitated the filing of the terminals into flat ends as shown 

 in Fig. 2. Even when the magnetic field was raised to 35000 

 ^ gauss, these pieces were not found to be attracted by the 

 1 magnet poles. In this investigation, as the zinc spectrum 

 for determining the field was photographed simultane- 

 ousty, o?ie of the terminals ivas always a z'mc rod of the same 

 diameter. '•* 



Similary as mentioned in man}'- published papers, 

 condensers were connected parallel in the spark circuit, 

 which also contained selfinduction coils. In my experi- 

 l^ig-2 • nient, three Leyden jars, each of which was about 0'00404 

 micro-farad, were connected in parallel and the whole was inserted 

 parallel to the spark circuit. Afterwards, on tlie advice of 

 Professor Nagaoka, I introduced another spark gap into the spark 

 circuit in addition to the selfinduction coils. This is recommen- 

 dable, especially in the case of long exposures. Very small self- 

 induction was sufficient in vay experiment, the sound of the 

 spark retained its shrillness, especially after the auxiliar}" spark 

 gap was introduced in the circuit. 



The spark gap of the light source varied from 1 to 3 mm. as 

 the pole-pieces of the electromagnet were changed. From a long 

 spark gap, I could get a brilliant light and a reduction in time of 

 exposure was rendered possible. 



1) When I read this paper at the ordinary meeting- of the Physico-uiathematil Society of 

 Japan on the 8th of March, Professor Nagaoka put the followin»- question to me : 



"The non-magnetic nickel-steel can positively have no effect upon the strength of the 

 magnetic field in which the spark is discharged. But the iron dnst grains scattered from the 

 end of the spark electrodes are attracted uy the magnet poles. How have you disj^oscd of the 

 influence of this dust upon the magnetic fields ? " 



I answered : " In order to get rid of this influence, I broke the magnetizing current and 

 completely removed the dust several times during the photographing. Moreover, in my 

 experiment, as the /ine line 4680"138 was simultaneously photograiihcd to deterenine the field, 

 the change of the field due to these powders, if any, also afl:ected the separation of this zinc 

 line at the same time ; in this manner the real value of th<} magnetic field in which the centre 

 of vibration of iron and nickel spectra is found, was obtained. To determine the field 

 accurately is one of the chief purposes of my experiuient." 



