626 Mr. J. Wilson Swan [May 20, 



ores, and the fusion and welding of metals. Electro-metallurgy has 

 in fact grown so large and many-branching, that it is impossible to 

 treat it in a complete manner in a single hour. 



; One of the latest developments is electric welding. This, in 

 one of its forms, that invented by Elihu Thomson, has recently 

 been so thoroughly explained and demonstrated by Sir Frederick 

 Bramwell, that it is not necessary for me to do more than mention 

 it as belonging to the subject. 



There is also another species of electric welding — that of Dr. 

 Benardos — in which the electric arc is used after the manner of a blow- 

 pipe flame, to obtain the welding of such forms and thicknesses of 

 iron, steel, and other metals, as would be difficult or impossible to 

 weld in any other way ; and not only is the electric blow-pipe used 

 for welding, but also for the repair of defects in steel and iron 

 castings, by the fusion of pieces of metal, of the same kind as the 

 casting, into the faulty place, so as to make it completely sound. 

 This new kind of electric welding, as improved by Mr. Howard, 

 is now of sufficient importance to entitle it to the full occu- 

 pation of an evening. I therefore propose to leave it for detailed 

 description to some other lecturer, and content myself with calling 

 your attention to the interesting collection of specimens on the table, 

 and in the Library (lent by Messrs. Lloyd & Lloyd), showing the 

 results of this process. 



Even with this curtailment, the extent of the field is still too 

 great, and I must reduce it further by omitting a considerable section 

 of that portion which relates to the extraction of metals from their 

 ores, and, in this connection, only speak of the extraction of 

 aluminium. 



But, in the first place, I am going to speak of the deposition 

 of copper, and you will pardon me if I treat it as if you were un- 

 acquainted with the subject. 



One of the wonderful things about the electro-deposition of 

 copper, and in fact any other metal deposited from a solution of its 

 salt in water, is, that bright, hard, solid metal, such as we are 

 accustomed to see produced by means of fusion, can, by the action 

 of the electric current, be made to separate from a liquid which has 

 no appearance of metal about it. 



The beginning of every electro-deposition process is the making 

 a solution of the metal to be deposited. I am going to dissolve a 

 piece of copper, the most elementary of all chemical operations, but 

 I want to make it quite clear where the metal to be deposited comes 

 from — to show that it is actually in the solution, and actually comes 

 out of it again ; for that is an effect so surprising, that it requires 

 both imagination and demonstration to make it evident. There is 

 projected on the screen a glass cell containing nitric acid. Mr. 

 Lennox will put into it a piece of copper. He has done so; it 

 quickly disappears, and a blue solution of copper nitrate is formed. 

 Now, if I pass an electic current through this solution, or through 



