198 Mr. Armstrong's Account of a 



figure. Under these circumstances you will perceive that the 

 tubes in the glasses numbered 1 . 3. 5. 7. and 9 contained ne- 

 gative poles, and that the remaining tubes contained positive 

 poles. 



Upon setting the machine to work, a stream of small bubbles 

 immediately began to rise from all the wires, and it soon be- 

 came evident that the gas which collected in the tubes con- 

 taining the negative poles, occupied exactly twice the volume 

 of that which was evolved from the positive poles. In the 

 course of two or three minutes the red liquid in number 9, 

 which you will observe consisted of nothing but distilled water 

 and acidified litmus, became blue around the wire in the tube; 

 while the blue liquid in number 10, consisting only of water 

 and blue litmus., was to the same extent changed to red. As 

 the process continued a similar change began to take place in 

 numbers 5 and 6, containing the solutions of sulphate of soda, 

 and in numbers 7 and 8, containing the solutions of sulphate 

 of magnesia ; but the transition from blue to red, and from 

 red to blue, was not nearly so rapid in these vessels as in 9 

 and 10, where no salt was present, to yield by decomposition 

 an acid at the one pole, and an alkali at the other. 



As soon as the pressure in the boiler had run down from 75lbs. 

 to 40lbs. on the square inch, the steam was shut off until the 

 original pressure was re-attained, when the machine was again 

 put in action ; and by repeating this operation several times, 

 I obtained as much gas in each of the tubes containing the 

 negative wires, as occupied nearly an inch from the top ; and 

 half that quantity by measure in each of the tubes containing 

 the positive wires. 



At the close of the experiment the change of colour from 

 red to blue in number 9, and from blue to red in number 10, 

 was perfect, and extended to the whole of the liquid in each 

 of those glasses as well as in the tubes contained in them. In 

 the other glasses, containing the solutions of sulphate of soda 

 and sulphate of magnesia, the change of colour was also con- 

 siderable, but not nearly so much so as in 9 and 10, although 

 at the beginning of the experiment the quantity of colouring 

 matter in all these glasses had. been the same. 



The proportions in which the gases were evolved from the 

 two poles, sufficiently indicated them to be hydrogen in the 

 one case, and oxygen in the other ; and it is scarcely neces- 

 sary to say that upon examination they proved to be such. 



I could perceive no difference in the quantity of gas, of the 

 same kind, which had collected in the different tubes, and the 

 decomposition seemed to be neither accelerated nor retarded 

 by making a small interruption in the conducting wire, so as 



