Applied Science 795 



trains of 800 tons weight over the mountain ranges of the Alps; it 

 will flash its wireless messages across the Atlantic at the speed of 

 186,000 miles a second; it will supply all the light and heat the 

 greatest city could want. Long submarine electric cables connect 

 the most distant lands, but such cables become more and more 

 dispensable. You can converse with a person in Paris without 

 using wire or cable; you can talk to an air pilot hidden behind 

 the clouds. 



Some of our greatest industrial undertakings are solely de- 

 voted to Electrical Engineering practice, and in almost every 

 phase of industry it plays a part: in the coal mine we have electric 

 coal-cutters, haulages, and winding machinery; in the modern 

 iron foundry the electric furnace which will produce tempera- 

 tures up to 6,000 F. ; in the Engineer's shop the electric arc for 

 welding all manner of metals and alloys. 



In factories steam power and the mechanical transmission by 

 shafting and belt is almost displaced by electric motors driving 

 separate machines, or groups of machines; and even for the 

 propelling of ships, electric energy transformed from the 

 mechanical energy of the steam turbine has been applied success- 

 fully. We cook by electricity, do our laundry- work by electricity, 

 sweep our rooms by electricity, even the dentist's tiny drill is 

 whirled round by electricity. We have electro-magnets, power- 

 ful enough to lift ten tons of scrap iron ; the medical man may use 

 a magnet to extract fragments of steel from a workman's eye. 



Ease of Transmission 



The cause of the enormous vogue of electrical power is to be 

 found in the fact that energy can be transmitted and distributed 

 in its electrical form very cheaply and efficiently. Where distances 

 are considerable, electricity has the field to itself. If a large 

 amount of energy has to be transmitted to a point, say, 100 miles 

 away, the alternatives are : air under pressure, water under pres- 

 sure, and electricity. For the first would be required huge pipes, 





