Q Art. 7. — K. Yamada : 



(G) Paget process Plate, (7) Chromo Isolar, (8) Wratten and 

 Wainwright panchromatic plates, (9) Seed 27, (10) Agfa-Trocken- 

 Platten, (11) Schleussnerplatten, (12) Cramer, (13) X Ray plate 

 and (14) llford Process Plate. Of these fom-teen kinds, I found 

 the "llford Process Plate" the most recommendahle for such 

 accurate purposes. The peculiarity of this plate is its fine grain, 

 though it has the drawback of requiring long exposure. 



The developer Avas in almost all cases " Agfa Rodinal " and 

 afterwards " Azol," with the addition of a few drops of potassium 

 bromide. A hydroquinone developer w^as also used, but it had no 

 advantage over those above mentioned. 



6. Identifications of Lines. Tlie identification of lines was 

 not so easily worked out when three orders, the 3rd, 4tli and 5th 

 overlapped on a photographic plate. At first I photographed iron 

 spectra together with À : 4358*58, 4078*05 and 4046*78 of mercury 

 lines. By the aid of this plate, I found to what region these 

 spectra belong and by the help of Buisson and Fabry's charts 

 inserted in "Recueil de Constantes Physiques (1913)", I could 

 easily identify the lines and from the tables of line spectra'^ and 

 those of iron lines'^ the values of weve-length -in international 

 unit are easily known. When two or three orders overlap on a 

 plate, a mere calculation with the help of the tables enables us to 

 detect the value of wave-length. 



7. Determination of the Magnetic Field. The magnetic separa- 

 tion of zinc line >?.: 4680' 138 has been accurately examined and 

 many experimenters have used it to determine the magnetic field. 

 One of the chief purposes of this experiment was the simultaneous 

 photography of zinc and iron lines. The groups " g," " h," "i" 

 and "j" were taken in this manner. But the simultaneous 

 photograph}^ thus obtained limited the number of lines, and I was 

 obliged to photograph tlie zinc lines before and after taking the 

 iron lines. The group "e" and "f" are those just mentioned. 

 The ranges and orders pliotographed on these plates are given in 

 Plates 1. and 11. 



1) Kayser, Handbuch der Spectroscopie, VI (1912) pp. 935-1033. 



2) Kayser, ditto, pp. 896-926. 



