Koenig also made a very ingenious modification of the siren for the
purpose of enabling Seebeck to sound simultaneously notes whose
vibrations had any given ratio. It is furnished for this purpose with
eight disks, each of which contains a given number of circles of
holes arranged at different angular distances. A description of this
instrument, which is also the property of the Stevens Institute, and of
Seebeck's experiments is thus given in a letter by Koenig himself.


I.

_Effects produced when the isochronism of the shocks is not perfect_.

A.

In order to produce a note, the succession of shocks must not deviate
much from isochronism.

If the isochronism is but little impaired, we obtain a note
corresponding to the mean interval of the shocks.

If the intervals between the shocks are alternately t and t', and if the
difference between t and t' is slight, we obtain the two notes t+t' and
(t+t')/2. If the intervals between the shocks are alternately t, t', and
t'', we obtain the two notes t+t'+t'' and (t+t'+t")/3.

Disk No. 1 has--

On circle No. 1 12 holes, angular distances t=30 deg.