Decomposition of IVater Inj Galvanism. 1 7 1 



dlty. Tvvo days before the experiment ended, I placed that 

 6Qd of the tube which had the gold wire at the upper end of 

 the trough, and very soon the platina which had rcmamed 

 brioht became black, an<l, when magnified, had the appear- 

 ance of black powder covering its surface, Irom the end to the 

 height ot the gold wire. The glass tube was m the torm of 

 the sketch sent herewith (Plate V. fig- C) The Imes on 

 the inside represent the two wires; ab the gold wire, and 

 cd the plaiina wire. 



This result made a repetition necessary in a more accurate 

 manner. Accordingly, I took another clean glass tube bent 

 in the same form, but I substituted, instead of the gold wue 

 a Z', a platina wire,so that both wires were of the same metal, 

 and introduced distilled water. After tl>is apparatus had 

 stood with its end a in connection with the zinc end ot the 

 trouah three davs, the short platina wire assumed the colour 

 of goU, and the Igng one began to grow black from the low or 

 end to the height of th.e short wire, and contmued so for the 

 space of three weeks. When about one-thu'd oi the water 

 had disappeared, 1 connected the lower end of the lube with 

 the copper end of the trough, and in the space of one day 

 the black powder left the Icnn; wire perfectly bright, and the 

 chort one became black. In the space of two days that por- 

 tion of the long wire to the height of the short one obtained a 

 .yellowish <rold-like tinge. Both remained so for three days ; , 

 uhcn I pUced them in their first situation: the black powder 

 left the short wire, and the long one became black I im- 

 mersed in the remaining water a slip of blue test paper ; the 

 colour was chanaedj so that I make no doubt but that, when 

 the operation is continued till half the water disappears, it 

 will give as strong signs of acidity as the former. 

 ■ You will observe that the ends of the wires are placed pa- 

 rallel to each other ; 1 found that situation to be most fa- 

 vourable to the production of gas : perhaps, if they were 

 placed with their ends opposite each other, the change of 

 colour would not take place. 



I am respectfully yours. 



No. 64, robnd-strcet. JOUX CuTHUERTSON. 



\h\Ti.h '/J, IBOG. 



XXX. No- 



