NO. 2 



HISTORY OF ELECTRIC LIGHT SCHROEDER 



25 



flow through a coil surrounding each permanent magnet to further 

 strengthen the magnets. Pulvermacher in 1849 proposed the use of 

 thin plates of iron for the bobbins, to reduce the eddy currents gen- 

 erated in the iron. Sinsteden in 185 1 suggested that the current from 

 a permanent magnet machine be used to excite the field coils of an 

 electro-magnet machine. 



In 1855 Soren Hjorth, of Copenhagen, Denmark, patented a 

 dynamo having both permanent and electro-magnets, the latter being 



Siemens' Dynamo, 1856. 



This dynamo was an improvement over others on account of the 

 construction of its " shuttle " armature. 



excited by currents first induced in the bobbins by the permanent 

 magnets. In 1856 Dr. Werner Siemens invented the shuttle wound 

 armature. This consisted of a single coil of wire wound lengthwise 

 and counter sunk in a long cylindrical piece of iron. This revolved 

 between the magnet poles which were shaped to fit the cylindrical 

 armature. 



THE FIRST COMMERCIAL INSTALLATION OF AN ELECTRIC LIGHT 



In 1862 a Serrin type of arc lamp was installed in the Dungeness 

 lighthouse in England. Current was supplied by a dynamo made by 



