NO. 2 



HISTORY OF ELECTRIC LIGHT — SCHROEDER 



15 



In 1840 Bunsen, the German chemist who invented the bunsen 

 burner, devised a process for making hard dense carbon pencils which 

 lasted much longer than the charcoal previously used. The dense 

 carbon from the inside of the retorts of gas making plants was ground 

 up and mixed with molasses, moulded into shape and baked at a high 

 temperature. Bunsen also, in 1843, cheapened Grove's battery by 

 substituting a hard carbon plate in place of the platinum electrode. 



Thomas Wright, an Englishman, was the first to patent an arc lamp. 

 This was in 1845, and the lamp was a hand regulated device consisting 



Wright's Arc Lamp, 1845. 



This lamp is also only of interest as the first arc lamp on which a 

 patent (British) was granted. Four arcs played between the five car- 

 bon discs. 



of five carbon disks normally touching each other and rotated by clock- 

 work. Two of the disks could be drawn outward by thumb screws, 

 which was to be done after the current was turned on thus establishing 

 four arcs, one between each pair of disks. The next year, 1846, W. E. 

 Staite, another Englishman, made an arc lamp having two vertical 

 carbon pencils. The upper was stationary. The lower was movable 

 and actuated by clockwork directed by ratchets which in turn were 

 regulated by an electro-magnet controlled by the current flowing 

 through the arc. Thus the lower carbon would be moved up or down 

 as required. 



Archereau, a Frenchman, made a very simple arc lamp in 1848. 

 The upper carbon was fixed and the lower one was mounted on a 



