hem
with chemical agents while under the objective.

While I am aware that this method is not wholly new, I am satisfied that
comparatively little work has been done in this direction, and that a
wide field is still open for future research.

As microscopists, we have to fortify ourselves in every way that will
sustain, by truthful work, the value of the microscope as a means of
research, sometimes conducting our experiments under the most trying
circumstances. Fibers may be so treated by experts as to make it
difficult to determine how their changed appearance has been effected,
and it may happen in this age of experiment and of fraud that important
decisions in commercial transactions and in criminal cases may depend on
our observations.

DETECTION OF A FRAUD.

A case in point will illustrate this. While Dr. Dyrenforth was chief of
the chemical division of the U.S. Patent Office, a person applied for a
patent on what he called "cottonized silk," inclosing specimens. He
claimed that he had discovered a mode of covering cotton fiber with a
solution of silk which could be woven into goods of various kinds; in
order to satisfy the public of the reality of his invention, he placed on
exhibition, in various localities, specimens of silk-like goods in the
form of ribbons in the web and skeins of thread, representing them to be
"cottonized silk."

Dr. Dyrenforth was not satisfied that the so-called discovery was an
accomplished fact, and he forwarded a few fibers of the material to the
division of which I have charge for investigation. I subjected them to my
usual tests, and found them to consist of pure silk, and I so reported to
Dr. Dyrenforth, who rejected the application for a patent. The microscope
was thus usefully employed to protect capitalists from imposition.

METHODS EMPLOYED.

It may be well to state briefly the methods I employed in detecting the
real character of the material. The fibers were first viewed under plain
transmitted light, secondly, polarized light and selenite plate. Since
silk and cotton are polarizing bodies, "cottonized silk," if such could
be made as described, would give, in this case, the prismatic colors of
both fibers, and the complementary colors would differ greatly because of
the great disparity of their respective polarizing and refractive powers.

The fact will be observed that a cotton fiber presents the appearance of
a twisted ribbon when viewed by the microscope, while