50 MR. J. P. JOULE ON THE 



the neighbourhood of, the juncture, and seriously impair the 

 quality of the iron at those points. 



It occurred to me some months ago that it might be possi- 

 ble to employ the calorific agency of the electric current in 

 the working of metals. By the use of a voltaic battery there 

 appeared to be no doubt but that small pieces of metal could 

 be fused into one lump. If so, it was obvious that by em- 

 ploying a battery of adequate size the largest masses of 

 wrought iron could be produced, the question resolving itself 

 simply into one of cost. It was not before the last month 

 that I had an opportunity of witnessing an experiment on a 

 small scale. It was performed in the laboratory of Professor 

 Thomson. He surrounded a bundle of iron wires with char- 

 coal, and, after transmitting a powerful current through it for 

 some time, the wires were found in one part to be completely 

 fused together. 



More recently I have made several experiments in which 

 the wires were placed in glass tubes, surrounded with char- 

 coal, &c. With a battery of six Daniell's cells I have thus 

 succeeded in fusing several steel wires into one, uniting steel 

 wires with brass, platina with iron, &c. I doubt not but that 

 in many instances the process would advantageously supersede 

 that of soldering, especially when, for thermo-electric or other 

 purposes, it is desirable to join metals of difficult fusibility 

 without the intervention of another metal which melts at a 

 lower temperature. 



Having demonstrated the possibility of obtaining perfect 

 junctions by means of the voltaic current, let us inquire what 

 expenditure of battery materials would be necessarily in- 

 volved. In the outset it may be remarked that were not heat 

 continually removed, by conduction, convection, and radia- 

 tion, from a wire carrying a current of however low a degree 

 of intensity, the wire would ultimately attain an excessively 

 high temperature on account of the continuous augmentation 



