DISRUPTIVE DISCHARGE— POSITIVE AND NEGATIVE BRUSH. 123 



1478. Thus we see that, notwithstanding there is a general difference in favour of 

 the superiority of the positive brush over the negative, that difference is at its maxi- 

 mum in nitrogen and air ; whilst in carbonic acid, muriatic acid, coal gas, and oxygen 

 it diminishes, and at last becomes almost nothing. So that in this particular effect, 

 as in all others yet examined, the evidence is in favour of that view which refers the 

 results to a direct relation of the electric forces with the molecules of the matter con- 

 cerned in the action (1421. 1423. 1463.). Even when special phenomena arise under 

 the operation of the general law, the theory adopted seems fully competent to meet 

 the case. 



1479. Before I proceed further in tracing the probable cause of the difference be- 

 tween the positive and negative brush discharge, I wish to know the results of a few 

 experiments which are in course of preparation : and thinking this Series of Researches 

 long enough, I shall here close it with the expectation of being able in a few weeks 

 to renew the inquiry, and entirely redeem my pledge (1306.). 



Royal Institution, 

 Dec. 23rd, 1837- 



r2 



