174 president's address — section h. 



its employment must completely change; for cities, no matter 

 how fortified, will be completely open to attack, and treaties not- 

 with>tanding the destruction of non-combatants and of private 

 property will be appalling. 



In conclusion, I would refer to the long distance transmission of 

 power. Passing over as experimental the now historical installation 

 at Frankfort, where 300 horsepower was electrically transmitted 

 108 miles, with a stated efficiency of 73 per cent., we find that the 

 adoption of the high tension alternating current system has ren- 

 dered it possible to transmit power over long distances with com- 

 mercial success. An electromotive force of 10,000 volts is now 

 recognised as a safe pressure if proper precautions be used. With 

 high pressures the cross section and cost of conductor is greatly- 

 reduced. The smallest sized wire having the necessary strength 

 for line work (No. 6, B. and S.) will, at 4,000 volts, transmit 100 

 horsepower ten miles with 80 per cent, efficiency. When pressures 

 exceeding 5,000 volts are employed it is advisable, on account of 

 difficulties connected with the insulation of the machines, to make 

 use of transformers, the current being raised for transmission at 

 the generator and again reduced at the motor terminals. As 

 transformers having an efficiency of 97 per cent, are now con- 

 structed the loss from this arrangement is insignificant compared 

 with the saving in cost of the conductor. 



The want of a perfected alternating-cm-rent motor has alone 

 delayed the rapid extension of this system ; but this difficulty has 

 apparently been completely overcome by the recent inventions of 

 Nicholas Tesla, and has been reduced to a minimum in an instal- 

 lation which has for the last two years been in regular work in 

 America. 



At the Gold King Mine, Colorado, power was required for 

 -operating crushers and stamps; fuel could only be procured from 

 long distances at enormous cost, but a few miles from the mine 

 Avater power was avadable ; the intevening country, however, was 

 so rough and so often snowed up that no ordinary means of trans- 

 mission could be made use of. Electricity was therefore adopted. 

 The plant consists of a Pelton wheel driving an alternating-current 

 generator. The current is carried by a bare wire up the mountain 

 side to the mine at a height of 2,500ft. ; here it drives a 100 

 horsepower synchronou.s motor, which is started by the assistance of 

 a small motor of the Tesla type. The efficiency of the system was 

 found on test to be 83A- per cent, at full and 74 per cent, at half 

 load, losses in generator and motor, but not those of conductor, 

 included. So satisfactory has been the practical working of the 

 plant that a 750 horsepower generator and a 300 horsepower and 

 some smaller motors have lately been added. 



Long distance transmission for lighting purposes has for the last 

 three years been in satisfactory operation at Portland, Oregon. 

 The falls of the Willamette River, thirteen miles from Portland, 



