56 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76 



INCANDESCENT LAMP DEVELOPMENTS, 1 884- 1 894 



In 1884 the ring of plaster around the top of the base was omitted ; 

 in 1886 an improvement w^as made by pasting the filament to the 

 leading-in wires with a carbon paste instead of the electro-plating 

 method; and in 1888 the length of the base was increased so that it 

 had more threads. Several concerns started making incandescent 

 lamps, the filaments being made by carbonizing various substances. 

 " Parchmentized " thread consisted of ordinary thread passed through 

 sulphuric acid. " Tamadine " was cellidose in the sheet form, punched 





Standard Edison Lamp, 1884. 



The rin^ of plaster around 

 the neck of previous lamps was 

 omitted. This lamp is in the 

 exhibit of Edison lamps in the 

 Smithsonian Institution. 



Standard Edison Lamp, 1888. 



The length of the base was 

 increased so it had more 

 threads. This lamp is in the 

 exhibit of Edison lamps in the 

 Smithsonian Institution. 



out in the shape of the filament. Squirted cellulose in the form of a 

 thread was also used. This was made by dissolving absorbent cotton 

 in zinc chloride, the resulting syrup being squirted through a die into 

 alcohol which hardened the thread thus formed. This thread was 

 washed in water, dried in the air and then cut to proper length and 

 carbonized. 



The filament was improved by coating it with graphite. One 

 method, adopted about 1888, was to dip it in a hydro-carbon liquid 

 before carbonizing. Another, more generally adopted in 1893 was a 

 process originally invented by Sawyer, one of the Americans who had 

 attempted to " sub-divide the electric light " in 1878-79. This process 



