434 



ENGINEERING ON THE FARM 



By means of these the lamps may be turned on or off at differ- 

 ent places. They will save a good many steps and make it 

 possible to get light when and where it is wanted. 



After University of Minnesota 



Fig. 331. Method of attaching feed wire to glass insulator on a pole 



Incandescent lamps. For years the carbon-filament lamp 

 was the only kind on the market. The tantalum lamp was 

 invented, but soon was followed by the tungsten. The latter 

 lamp has displaced the tantalum almost entirely, and the 

 carbon lamp is now being used only by those who have not 



had occasion to appreciate 

 the higher efficiency of the 

 tungsten lamps. Three 

 tungsten lamps can be 

 operated for the price of 

 one carbon. It is therefore 

 folly to buy new carbon 

 lamps, and it is a question 

 whether you can afford to 

 burn your old carbon 

 lamps as an attempt at 

 economy, except where a 

 lamp is used very, very 

 little, as, for instance, in the attic. The nitrogen tungsten 

 further increases the efficiency of the lamps. 



SUMMARY 



If it is desirable to install an isolated lighting plant, it is 

 important to recognize in advance the fact that if the plant 



After University o» Minnesota 



Fig. 332. Method of entering a building 

 to prevent water from following the 

 wire through 



