THE STRtlOTUilE OF THE NUCLEUS. 



41 



insure greater safety of observation. Each window may be replaced by an 

 aluminum window for X-rays, etc. G is the gauge, d the exhaustion, cf the influx 

 tubulure. When nuclei are to be introduced, the filter,/', is removed. 



20. Preli'mitiary observations. Single drum. — The following are a few 

 results with the single drum, the window being screened off to a small circle : 



TABLE r4.— AXIAL COLORS SEEN IN THE SINGLE DRUM, 77 cm. LONG, 30 cm. 

 DIAMETER AT BASE. EXHAUSTION 76-50 cm. PUNK NUCLEI. 



The following I'esults were obtained with a ground glass sci-een, affording a 

 laro-e patch of flame coloi-. The contrasts of color between the flame and the 



coronal center are again the marked feature : 



TABLE IS.- AXIAL COLORS SEEN IN THE SINGLE DRUM. CONSTANTS AS IN 



TABLE 14. GROUND GLASS SCREEN. 



The exhaustion proceeds too rapidly here to bring out all the coronal sequences. 

 Intermediate cases are skipped, which is confusing. All color display begins with 

 a rush from the first flame and first corona to the last, as the particles increase in 

 size to a limit. Thereafter the phenomenon shows a tendency to reverse, but it is 

 much slower, soon obscured, and then vanishes. Owing to the difficulty of deciding 

 between these fleeting color contrasts, I have in the following table included a 

 group of incidental results for different exhaustions made at different times. 



