By the use of a lens made of
quartz covered with a thin film of metallic silver, there has been
developed a practical means of making photographs by the invisible
rays of light above the spectrum--these ultraviolet rays. The
quartz lens is necessary, because these rays will not pass through
ordinary glass, while the silver film acts as a screen to cut off
the ordinary light rays and those below the spectrum. By this
means, most white objects are photographed black and even
transparent objects like glass are black.
"I obtained the copy of this will, but under the condition from
the surrogate that absolutely nothing must be done to it to change
a fibre of the paper or a line of a letter. It was a difficult
condition. While there are chemicals which are frequently resorted
to for testing the authenticity of disputed documents such as
wills and deeds, their use frequently injures or destroys the
paper under test. So far as I could determine, the document also
defied the microscope.
"But ultraviolet photography does not affect the document tested
in any way, and it has lately been used practically in detecting
forgeries.
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