1851 Great Exhibition: Official Catalogue: Class X.: Abel Siccama
535. SICCAMA, ABEL, 135 Fleet Street — Inventor, Patentee, and Manufacturer.
Diatonic flutes, retaining the old system of fingering while affording numerous additional fingerings, on a system strictly based upon acoustic principles. Their tone is said to be powerful and brilliant. They are easier of execution, and therefore require less exertion to play than the ordinary flute. There are three middle C's on this flute, all of the same quality, and perfectly in tune.
[There are two scales commonly understood — the DIATONIC and the CHROMATIC: the first proceeding by tones and semitones, and the second by semitones alone. But there is a third scale, the ENHARMONIC, that is not so well known. It can be thus explained: Notes have their pitch determined by a certain number of vibrations. By this we find that C# and Db), though one sound on a keyed instrument, have distinct sounds in reality. The Enharmonic scale then is a succession of every possible note according to its vibratory intensity, e. g. G, Db, C#, D, Eb, D#, E, and so on.—H. E. D.]