34 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, J^ 



Wallace- Farmer Arc Lamp, 1875. 



This " differentially controlled " arc lamp consisted of two slabs of 

 carbon between which the arc played. In the original lamp the car- 

 bon slabs were mounted on pieces of wood held in place by bolts, 

 adjustment being made by hitting the upper carbon slab with a ham- 

 mer. This lamp is in the collection of the Smithsonian Institution. 



%i|i^ 



Wallace-Farmer Dynamo, 1875. 



This was the first commercial dynamo used in the United States for 

 arc lighting. This dynamo J^ in the collection of the Smithsonian 

 Institution. 



