Applied Science 815 



whole output of our coal-mines per annum, represent the amount 

 that would have to be fed to boilers to produce the energy of 

 water already doing service. The world's total water-power 

 would on this basis exceed that obtainable from the world's coal 

 output in 1913! 



It may be that the development of water-power will in the 

 future affect the centre of gravity of the world's industries, for 

 these tend to move towards cheap power. A rather interesting 

 illustration presents itself. In North Sweden are vast deposits 

 of iron ore, formerly mined for smelting in England and other 

 coal-producing countries. But Sweden, though poor in native 

 coal, is rich in water-power, now being developed to run great 

 electric furnaces in which the ore will be converted into iron and 

 steel, thus enabling her to compete in the world's markets under 

 favourable conditions. Her waterfalls have given Norway a 

 new industrial importance. Who shall say that a country like 

 Brazil, with its estimated 26,000,000 h.p., and British Guiana, 

 the Zambesi Basin, New Zealand, and other naturally favoured 

 countries, may not in future years become industrially important, 

 thanks to the energy of falling water? 



Electric Lighting 



It is unnecessary to discuss what we owe to electricity in 

 the form of light ; it is evident to every one. If an electric current 

 be forced through a very fine wire able to stand extremely high 

 temperatures without melting, the resistance encountered causes 

 the generation of heat, which is partly converted into that form 

 of energy called light. In this way we get the incandescent 

 electric lamp, which is simply a fine wire of tungsten enclosed 

 in a glass bulb, from which all the air is exhausted to prevent 

 the metal being burnt by combination with oxygen, the wire 

 being made white-hot by the current. We may admit, after 



