Electrolysis across Glass. 127 



sary to say that, according to received opinions and experiments, 

 no current passes and no electricity takes place. I was led by 

 some theoretic considerations to think that this rule might not 

 be without an exception ; and the following experiment realized 

 my views. 



A Florence flask, well cleaned and dried, was filled two-thirds 

 full of distilled water with a few drops of sulphuric acid added 

 to it, and placed in an outer vessel containing similar acidulated 

 water which reached to the same height as the liquid in the 

 interior. A platinum wire was passed through a glass tube, one 

 end of which was hermetically sealed to the platinum, but so as 

 to allow a small portion of the wire (about 2u^ n °f an mcn ) to 

 project J the other end of the wire was passed through a cork, and 

 the cork fitted to the mouth of the flask ; when the cork was 

 introduced, the projecting end of the platinum wire was three- 

 quarters of an inch below the surface of the interior liquid ; a 

 similar coated wire was dipped into the outer liquid, and this 

 and the wire which passed through the cork were brought 

 respectively into connexion with the extremities of the secondary 

 coil of a Ruhmkorff apparatus. Upon the latter being excited 

 by the battery, a stream of minute bubbles arose from both the 

 platinum points, proving clearly that electrolysis took place not- 

 withstanding the interposition of the glass. The portions of the 

 flask above the liquid, both outside and inside, were perfectly dry, 

 so that there could have been no communication of the current 

 over the surface of the glass. This was further proved by re- 

 moving the outer wire a short distance from the surface of the 

 water, when sparks passed nearly equal in length to those which 

 took place between wires from the terminals. As the outer wire 

 was further removed, keeping it near the glass, the sparks passed 

 along the surface of the latter for a short distance ; and as it was 

 further removed they ceased, thus showing conclusively that 

 there was no passage of electricity over the upper and unwetted 

 surface of the glass. 



With distilled water unacidulated I could observe no effect of 

 electrolysis. 



With acidulated water and the same arrangement I could detect 

 no signs of electrolysis when, instead of the UuhmkorfF coil, an 

 intensity nitric acid battery of thirty cells was employed. 



In the first experiment the evolution of gas gradually dimi- 

 nished, and ceased after about twenty minutes' experiment ; but 

 upon intercepting communication with the battery for ten 

 minutes and then reconnecting it, the evolution took place again ; 

 or a recurrence of electrolysis could be produced by reversing 

 the direction of the current. 



When the flask, after twenty minutes' experiment, was removed 



