134 ELECTRICAL ADVANCE IN THE PAST TEN YEARS. 



little indication in the finislied product. As an instance, it may be 

 mentioned that the solid rubber tires of carriages are lie].d in place by 

 wires welded into bauds by electric welding macliines built for tlie pur- 

 pose. Similarly, carriage hardware, axles, wheel tires, parts of bicy- 

 cles, parts of machines, tools, and innumerable other articles are made. 

 Metal bands for pails, tubs, and barrels are now largely made by electric 

 welding. Even steel tubes for bicycles and vehicle frames are formed 

 by the same means; and new industries are based upon it. A curious 

 and instructive instance of the adaptability of electric methods to new 

 uses is seen in the annealing of armor for war vessels. A serious dififi- 

 culty arose in the application of armor plate having a hardened face and 

 known as harveyized armor. It was found almost impossible to drill 

 or cut holes in the face — an operation frequently rendered necessary 

 in the construction of an armored ship. Various methods of anneal- 

 ing or softening the spots where the j)late was to be drilled were tried, 

 with indifferent results. The construction of some of our battle ships 

 was delayed on account of this difficulty. It was overcome by a special 

 electric method, with appropriate machinery somewhat resembling that 

 used for electric welding, capable of heating to redness the desired 

 spots in the face of the heaviest armor plate, and of automatically reduc- 

 ing the heat of the spots so as to anneal them. The heating and con- 

 trol of the cooling is i)erfectly brought about, in spite of the enormous 

 mass of cold metal surrounding the portion under treatment. Together 

 with electric welding work, this armor annealing is a striking instance 

 of the extreme localization of heating in metal, i)Ossible only by the 

 delivery of electrical energy and its conversion into heat at the desired 

 point. In electric welding, the electric heat is sharply localized at the 

 weld itself, softenin'g and unitiiig the pieces; the operation being under 

 the same perfect control as in the armor annealing referred to. Before 

 the advent of the electric process, iron and platinum only were known 

 as the weldable metals. Afterwards, all metals became capable of 

 welding under electric treatment. 



Electric heating is now also applied in many other ways. There are 

 to be found electric cooking utensils, electric sad irons, electric solder- 

 ing tools, and similar devices; while many street cars are provided with 

 electric heat in winter. 



The chief bar to the employment of electricity for general heating 

 lies in the fact that in using coal to develop power by steam engines — 

 which power in turn is sent out as electrical energy — 85 to 90 per cent 

 of the heating value is lost in the boiler and engine. This loss is so 

 great as to make it undesirable, from the standpoint of cost, to recon- 

 vert the electric energy back into low heat, which can be more econom- 

 ically obtained from the direct use of burning fuel. 



Besides the technical and industrial development which has gone 

 on so rapidly in the electrical field, the science of electricity, considered 

 simply as a department of physics, has advanced very rapidly. It is 



