have their scales based upon the
displacement of the polarized ray produced by a quartz plate of a
certain thickness; others upon the displacement produced by an
arbitrary quantity of pure sucrose, dissolved and made up to a certain
volume and polarized in a certain definite length of column. It would
be very desirable to have an absolute standard set for polariscopic
measurements, to which all instruments could be referred, and in the
terms of which all such work could be stated. This commission has
information that an investigation is now in progress under the
direction of the German imperial government, having for its end and
purpose the determination of such data as will serve for the
establishment of an absolute standard. When this is accomplished it
can easily be made a matter of international agreement, and all future
forms of instruments be based upon it. This commission would suggest
that the attention of the proper authorities should be called to the
desirability of official action by this government with a view to
co-operation with other countries for the adoption of international
standards for polarimetric work. Until this is done, however, it will
be necessary for the Internal Revenue Bureau to adopt, provisionally,
one of the best existing forms of polariscope, and by carefully
defining the scale of this instrument, establish a basis for its
polarimetric work which will be a close approximation to an absolute
standard, and upon which it can rely in case of any dispute arising as
to the results obtained by the officers of the bureau.

For the instrument to be provisionally adopted by the Internal Revenue
Bureau, this commission would recommend the "half shadow" instrument
made by Franz Schmidt & Haensch, Berlin. This instrument is adapted
for use with white light illumination, from coal oil or gas lamps. It
is convenient and easy to read, requiring no delicate discrimination
of colors by the observer, and can be used even by a person who is
color blind.

This form of instrument is adjusted to the Ventzke scale, which, for
the purposes of this report, is defined to be such that 1 deg. of the
scale is the one hundredth part of the rotation produced in the plane
of polarization of white light in a column 200 mm. long by a standard
solution of chemically pure sucrose at 17.5 deg. C. The standard solution
of sucrose in distilled water being such as to contain, at 17.5 deg. C. in
100 c.c., 26.048 grms. of sucro