M. E. Goldstein on Spectra of Gases. 335 



that the discharge can be disruptive in one part of the circuit 

 and continuous in the other part. We must therefore investi- 

 gate the question whether the discharges go through adjacent 

 parts of the same circuit in the same rhythm or not, in order to 

 be able to decide whether Wullner's hypothesis can be correct. 



If we take an analogy in the now of an incompressible liquid, 

 the isochronism of the discharge in different parts of the same 

 circuit is self-evident.- The experimental investigation gave the 

 following results. 



The rotating mirror showed that if the exhausted tube was at 

 the same distance as the spark, both images were of the same 

 width. If the discharge through air under atmospheric pres- 

 sure begins, as shown by Lissajous, by a spark followed by the 

 aureola, the image of the spectral tube begins with a luminous 

 band, the width of which remains constant, whatever the velo- 

 city of the mirror may be. 



When the diseharg-e in the air consisted of several partial dis- 

 charges, the same number of narrow images of the tube were seen 

 at corresponding distances. 



The image of the discharge through a vacuum-tube is, when 

 the remaining circuit is metallic, very complicated, consisting 

 of fields of different brightness, &c. Two or more tubes put 

 into the same circuit, even if the gas in the different tubes 

 is chemically different (e. g. nitrogen and carbonic acid), always 

 give exactly the same image, showing in every detail the same 

 groups of illuminated fields and the same variation in bright- 

 ness. The exact coincidence of rhythm and intensity in the 

 same discharge, according to these experiments, is evident. 



A tube filled with carbonic oxide which is in my possession 

 allows only sparks to pass ; every discharge of the induction- 

 coil is subdivided into a greater or smaller number of sparks. 

 This tube was inserted in the circuit together with other tubes 

 containing nitrogen. These nitrogen-tubes separately allowed 

 a continuous discharge to pass ; but when the carbonic-oxide 

 tube was introduced, sparks only passed, the same number as in 

 the carbonic-oxide tube. 



A Leyden jar gives very strong sparks; the effect of the in- 

 duction-spark (which allows only a small quantity of electricity 

 to pass) will only show quantitative differences compared with the 

 discharge from a battery of Leyden jars, and will be about the 

 same as the discharge from a small jar. 



If the electricity goes through the whole circuit in the same 

 rhythm, the introduction of a small spark through air will have 

 the same effect as a condenser which is feebly charged. 



The introduction of a condenser changes the reddish colour 

 of the positive light seen in narrow tubes into blue. The intro- 

 duction of a spark will give the same result. 



2 A2 



