30 Mr. Alexander Siemens [Feb. 3, 



tific data in connection with this problem are as follows : A kilo- 

 gram of coal burnt to best advantage will give 8080 calories. The 

 same amount of coal consumed in a boiler will produce steam sufficient 

 for 1 H.P. for 1 hour, and this horse-power can generate electricity 

 at the rate of 660 watts, or about 570 calories, per hour. 



Assuming that in heating by burning coal, only a quarter of the 

 theoretical effect is attained, and taking the price of coal at 20s. per 

 ton, while the cost of a Board of Trade unit of electricity is 8d., it 

 would appear that a farthings worth of coal will produce as much heat 

 as 2 2d. worth of electricity. 



These figures apply to the conditions of life in London, where 

 fuel is abundant and power comparatively expensive ; elsewhere, in 

 Norway for instance, fuel may be expensive, and power, in the shape 

 of waterfalls, cheap. Under such altered conditions electricity may 

 with advantage be employed for heating purposes, by producing it 

 with the aid of water-power, and utilising the heat generated by it, 

 in special appliances. 



One of the most important industries of Norway is the making of 

 horseshoe nails, for which special machines have been constructed, 

 into which a heated rod of iron has to be fed. For this purpose the 

 rod is passed through a charcoal fire, placed close to the nail-making 

 machine, and a great deal of difficulty is experienced in maintaining 

 the rod at an even and suitable temperature. The apparatus placed 

 in front of you is designed to replace these charcoal fires, and its con- 

 struction is shown by the diagram on the wall. The essential part 

 of it is a hollow carbon, through which a current of electricity is 

 sent, heating the carbon to any desired temperature. In this appa- 

 ratus, a current of 400 amperes and 5 volts is used, equal to 2 Board 

 of Trade units per hour, which is supplied from a transformer, 

 the primary circuit of which is connected to the high-pressure mains 

 of the London Electric Supply Company. A diagram of the connec- 

 tions show r s that the two wires connected to the supply main are led 

 to a commutator on the table, by w r hich the current can either be 

 sent to the transformer of the heating apparatus, or to another one, 

 which will be mentioned later on. In order to prevent loss of heat 

 by radiation, the carbon is placed in a box filled with sand, and the 

 necessary precautions are taken to let the current pass through the 

 carbon only. After the carbon has become white hot, a rod of iron, 

 in passing through it, is rapidly heated, and the temperature it 

 attains depends on the speed at which it is fed forward. 



It would have been very inconvenient to bring a nail-making 

 machine here. With your permission, I will therefore ask Mr. 

 Williamson, who designed the apparatus, to show us how to make 

 spiral steel springs. 



By the side of the nail-rod heater stands a similar apparatus for 

 the heating of rivets, which is also illustrated by a diagram, and will 

 be shown in action. 



It is obvious that such an apparatus can be used in many places 



