Page 4 Page 5

Page 6

Six carbon arc lamps - state of the art for 1881. The lamps were topped with a shield protecting the lamps and diffusing the light downward, onto San Jose's golden streets.

Electricity was supplied to the lamps from a Number 6 Brush dynamo-electric light machine (9 hp) belonging to George Roe (San Jose Brush Co.) George's dynamo (same thing as a generator) was housed in Thomas Gillespies's planing mill on El Dorado St. (present location of the Greyhound Bus station). A steam engine provided 60 pounds of pressure that propelled a generator wheel at 840 rpm. "The same big steam engine that powered the mill by day turned the generator by night." Clyde Arbuckle

So why is there light?
Well sir, two carbon electrodes in each lamp were placed in proximity to each other - but not touching. Power was applied and electricity "arced" across the gap beween the electrodes. The tips of the carbons and the gap between them become super heated, and light was emitted as a consequence. The carbons become smaller and smaller as they burned and emitted light. It was a trick to keep the gap consistent as the carbons burned away from each other.

Even with 24,000 candle power the tower was not up to the task of lighting downtown San Jose effectively. The problem was distance. As any schoolchild can tell you, usefull light, when transmitted in free wave form, diminishes inversely as the square of the distance. Even if you concentrate or beam the light, you end up with only one fourth the light you emitted at every doubling of distance. By 1884 the towers lights were used only for weekends, holidays, and festive occasions.

In 1891, incandescent light bulbs replaced the carbon arc lamps.

Page 4  Page 5

Page 6