Art. 8.— Y. Takabashi : 



When the horizontal sht was opened wide only the prism spectrum 

 was observed at tlie camera, and then the sht was slowly closed 

 until the vertical lines contracted to dots of echelon spectra. Thus 

 many lines were photographed at a juxtaposition, admitting exact 

 comparison of the magnetic separations among these lines. Proper 

 adjustment of the inclination and position of the photographic 

 plate and the position of the planar Itehind the echelon spectro- 

 scope made it possible to photograph green lines in one and the 

 same exposure with violet lines, if we allowed the disturbing of 

 the sharpness of the prism specti'um, but the difference in the 

 intensity and the photographic sensitivity made it convenient to 

 separate the exposure into several steps, each lasting 10 to 3()0 

 minutes according to the magnetic held and the lines to be photo- 

 graphed. In some |)lates I have photographed the echelon spectra 

 of the whole region in one focus with disturbed prism spectrum, 

 and in other plates with sliarp prism spectrum, changing the posi- 

 tion of the planar from exposure to exposure. For the larger part 

 of the experiment a WoUaston prism AV Avas inserted between the 

 planar and the vertical slit, by which it was possible to photograph 

 both the parallel and perpendicular Zeeinan components at once. 

 For some exposures the Wollaston prism was removed and a nicol 

 was placed in fr(.»nt of the horizontal slit. Some photos were taken 

 without separating the polarized components to see if any dissym- 

 metry of the resolution exists, l)ut without any conclusive result. 

 The others were photographed without the planar to shorten the 

 time of exposure at the cost of small magnihcation. 



In order to make .the apparatus free from mechanical and 

 thermal disturbances, the whole arrangement was placed in a 

 cellar, and the l»ox containing the echelon grating was protected 

 by cork plates. On tine days, dry air was allowed to enter the 

 room through tlie windows; then shutting tlie windows and the 

 door tightly, the temperature in the room was kej)t as constant as 

 possible, and the image of the echelon spi'etva cHd not suffer any 

 sensible disturbance even if tlie exposure was eontinued during the 

 whole day. 



In order to eliminate errors arising from irregular contraction 



