RECENT WONDERS OF ELECTRICITY. 787 



the water, the elements of water oxygen and hydrogen are driven 

 asunder, and take refuge, as it were, in the right- or left-hand tuhe 

 respectively. To prove that these gases have been collected, if a 

 lighted match be placed over the hydrogen-tap, the hydrogen will 

 give evidence of its presence by inflammability ; but, if the match be 

 blown out and immediately presented to the tap of the tube contain- 

 ing the oxygen, that gas will make its presence evident by relighting 

 the match. The effect of the passage of electricity through water 

 is something like the effect which would be produced by a storm, 

 or other agency, in this room, which caused all the boys of this au- 

 dience to go to one side, and all the girls to go to the other except- 

 ing that in water there are always two parts of hydrogen to one part 

 or volume of oxygen. Not only does the current tear asunder the 

 oxygen and hydrogen of water, but it also breaks up the constitu- 

 ents of most of the chemical compounds, and the weight of material 

 decomposed per second is an exact measure of the work done and of 

 the current flowing. For instance, if we take a solution of sulphate of 

 copper and pass electricity through it, the solution is broken up into 

 copper and sulphuric acid, and, if a bunch of keys were put into the 

 solution while the electricity was passing through it, the keys would 

 receive a deposit of copper. If nitrate-of -silver solution were used 

 instead of the sulphate-of-copper solution, silver would be deposited 

 upon the keys or piece of metal inserted. Through the kindness of 

 Mr. Bolas I am able to show you an experiment of this kind, which 

 will enable me to give you a record of this evening's entertaiument. 

 I have here a large glass dish containing a liquid, which no doubt ap- 

 pears to you like water, but which is really a solution of the double 

 salt of cyanide of silver and potassium. In this solution I now place a 

 piece of sheet-copper, which you see has the usual appearance of cop- 

 per all over it. Now, while that plate of copper is inserted to one 

 half its extent in water, we will pass electric currents through the 

 liquid from the hand dynamo-machine on the table [experiment pro- 

 ceeding], which cause the cyanide of silver to break up into cyanogen 

 on one side and silver on the other ; and, if I take out the plate of cop- 

 per, you see there has been deposited upon its immersed surface a 

 coating of silver. Silver spoons and all the various kinds of electro- 

 plate wares receive their silver deposit in the manner I have just shown 

 you. Now, we will set this small dynamo-machine in action by turn- 

 ing its handle, thus converting the energy of the human body into 

 electric energy ; and we will immerse a quantity of brass buttons in 

 the liquid, which, when they have received their coating of silver, will 

 be laid aside, ready for distribution as a memento at the close of the 

 lecture. Through the kindness of Messrs. Elkington I am able to show 

 you the handsome specimens of electro-plating which hang on the walls 

 of the room, and which were plated at their works at Birmingham, by 

 a process exactly similar in character to that I have described, except- 



