o74 Prof. E. Wiedemann on the Behaviour of Gases 



nature of the electricity passing through, F the length of spark 

 included ; </, md 3 b, and mb denote that the wide tube was 

 dark, moderately dark, bright, or moderately bright. 



A. 



B. 









Heating. 





I 





Heating. 



P 





F 





m 



ji 



» 











Narrow.. J 



Wide. 



V 







Narrow. 



Wide. 



X 



+ 



o 



0-20 



007 



X 



+ 







0-19 



009 



— 



— 







017 



009 



— 









0-18 



009 



— 



+ 



5 



0-23 



018 



— 



+ 



5 



0-30 



0-13 



— 



— 



5 



018 



009 



— 



— 



5 



0-20 



010 



— 



+ 



10 



039 



0-26 



— 



+ 



10 



0-49 



016 



3-8 



— 



10 



0-27 



0-13 



— 



— 



10 



0-21 



011 



4- 







115 



0-38 md 



4 



-f 







1-12 



0-25 d 



— 



— 







1-35 



0-85 b 



— 



— 







1-36 



1-08 6 



— 



+ 



1 



0-95 



0-29 d 



— 



+ 



5 



1-22 



0-57 6 



— 



— 



1 



1-23 



0-91 6 



— 



— 



5 



1-50 



0-80 6 



— 



+ 



8 



111 



0-66 d 



5-3 



+ 







1-35 



0-20 tf 



— 





8 



103 



0-83 6 



— 



— 







1-62 



1-20 6 



73 



+ 







1-72 



0-73 d 



— 



+ 



4 



1-53 



0-41 mb 



— 



— 







2-25 



1-33 6 



— 



— 



4 



T76 



1-14 6 



— 



4- 



5 



1-85 



0-63 a 













— 



~~ 



5 



1-90 



1-25 6 



1 













These tables afford, in the first place, a confirmation of 

 the former results, inasmuch as in narrow tubes the heating- 

 is very nearly independent of the quantity of electricity 

 transmitted, especially at high pressures. Further, deviations 

 from this laiv occur, esjiecially with the positive discharge. In 

 the wide tube they are perceptible optically as well as therrni- 

 cally. By including sparks, a wide tube may be made dark 

 which was luminous before, whilst a still further increase of 

 the spark-length calls forth again an increase in brightness. 

 With this there goes hand in hand a diminution and subsequent 

 increase in the heating of the calorimeters, as the observations 

 at the pressure 3"8, for example, show. It is nearly indif- 

 ferent whether the electrode nearest to the wide tube is con- 

 nected with the source of electricity or with the earth. 



This peculiar behaviour of positive electricity becomes much 

 more marked when we use calorimeters with mercury instead 

 of turpentine. 



The following table gives a series of such comparative 

 measurements, which were made at very low pressures, whilst 

 the electrode nearest the wide tube was connected with the 

 machine : — 



