City of Light: The Story of Fiber Optics

GUIDING LIGHT AND LUMINOUS FOUNTAINS 21
in voltaic arcs of great power and intensity, for if more than one arc is
maintained with the same current of electricity, the light generated becomes
rapidly less, and therefore dearer, as the number of arcs or lights is increased.
It is in the nature of the electric current, therefore, that for the
economical generation of light it should be used in great intensity in one
point instead of small intensity in many points. 33
Wheeler examined every detail, down to the placement of screws holding
pipe segments together. At the heart of his idea were hollow glass pipes, clear
on the inside, coated with silver on the outside, then covered with asphalt to
prevent scratches and tarnish. They did not guide light by total internal reflection,
but instead relied on the strong reflection of light striking clear glass
surfaces at a glancing angle in air. Tilt a piece of glass as you look along its
surface, and you can see the effect. The glass doesn’t reflect all the light, but
neither do the shiniest metal mirrors. His drawing, shown in figure 2-4, is
an elegant masterpiece of Victorian patent art.
Solid glass rods didn’t enter the picture; Wheeler knew the clearest glass
on the market couldn’t carry light through a house. What he didn’t know
was that the incandescent bulb, invented the year before he filed his patent,
would make small lamps practical. His light pipes never got off the ground,
but the Wheeler Reflector Company did and made street lamp reflectors until
the late 1950s. 34
Illuminating Rods
A handful of other inventors tried guiding light short distances through glass
in the late 1800s. Most wanted to deliver light to hard-to-reach places. That
was difficult with gas or oil lamps, and even with early incandescent bulbs.
All generated far more heat than light, making them dangerous to put close
to most objects.
That was a serious problem for surgeons and dentists. They needed light
to see but didn’t want a hot lamp to burn themselves or their patients. In
late 1888, two men in Vienna adapted ‘‘the well-known experiment for showing
total reflection of light in a jet of water or in a glass rod’’ to illuminate
the inside of the nose and throat. They attached an electric lamp to one end
of a glass rod, which carried the light but not the heat, and put the other
end against the side of a patient’s throat. Enough light passed through the
skin for them to examine the larynx, and they thought the same approach
could illuminate body cavities during surgery. 35
A decade later, an Indianapolis man patented a dental illuminator that
used a curved glass rod to deliver light from a lamp into the mouth. 36 Interestingly,
he designed versions for both incandescent and acetylene gas lamps,
a reminder that electric lighting had not become standard even by the turn
of the century. Scientists likewise illuminated microscope slides with bent
glass rods to avoid drying out their specimens. In the 1930s, DuPont devel-