ELECTRICITY DURING THE NINETEENTH CENTURY. 853 



not tiike place. Henri Moi.ssan, a French scientist, well known for 

 his brilliant researches in electric furnace work, has even shown that 

 real diamonds can l)e made under special conditions in the electric 

 furnace. He has, in fact, probably practiced in a small way what has 

 occurred on a grand scale in nature, resulting- in diamond fields such 

 as those at Kimberley. One less problem is thus left to be solved. 

 The electro-chemical and kindred arts are practiced, not alone at 

 Niagara, but at many other places where power is cheap. Extensive 

 plants have grown up, mostly within the five years l)efore the close of 

 the centur}'. All of the great developments in this field have come 

 about within the last decade. 



The use of electricity for heating is not confined to electric fur- 

 naces, in which the exceedinglj^ high temperature obtainable is the 

 factor giving rise to success. While it is not likely that electricity 

 will soon be used for general heating, special instances, such as the 

 warming of electric cars in winter by electric heaters, the operation 

 of cooking appliances l>y electric current, the heating of sad-irons 

 and the like, give evidence of the possibilities should there ever be 

 found means for the generation of electric energy from fuel with such 

 high efiiciency as 80 per cent or more. Present methods give, under 

 most favorable conditions, barel}^ 10 per cent, 90 per cent of the 

 energy value of the fuel being unavoidably wasted. 



Another application of the heating power of electric currents is 

 found in the Thomson electric wielding process, the development of 

 which has practicall}^ taken place in the past ten A^ears. In this proc- 

 ess an exceedingly large ci\rrent, at very low^ electric pressure, 

 traverses a joint between two pieces of metal to be united. It heats 

 the joint to fusion or softening ; the pieces are pushed together and 

 welded. Here the heat is generated in the solid metal, for at no time 

 during the operation are the pieces separated. The current is usually 

 obtained from a welding transformer, an example of an extreme type 

 of stepdowm transformer. Current at several hundred volts passed 

 into the primary winding is exchanged for an enormous current at 

 only 2 or 3 volts in the welding circuit in which the work is done. 

 The present uses of this electric welding process are numerous and 

 varied. Pieces of most of the metals and alloys before regarded as 

 unwelda]>le are capable of being joined, not only to pieces of the same 

 metal, but also to difi'erent metals. Electric welding is applied on the 

 large scale for making joints in wires or rods, for welding wagon and 

 carriage wheel tires, for making barrel hoops and bands for pails, for 

 axles of vehicles, and for carriage framing. It has given rise to special 

 manufactures, such as electrically welded steel pipe or tube, wire 

 fencing, etc. It is used for welding together the joints of street-car 

 rails, for welding teeth in saws, for making many parts of bicycles, and 



