Source: http://en.wikipedia.org/
The Flageolet is a variation of the flute and similar to the recorder. The flageolet and recorder differ only with regards to fingerholes. The recorder has seven finger-holes in front and one thumb-hole at the back. The flageolet has four finger-holes in front and two thumb-holes at the back.
Acoustically the flageolet functions in the same manner as the flute and recorder. It is a pipe with holes that serve to shorten the frequency when opened.
The mouthpiece of the flageolet is known as a fipple. This piece has a narrow slit (windway or ducted flue) to concentrate the moving air column and has two outlets. Through one outlet air flows through the body of the pipe, while through the other (the lip or labium), which produces the Bernoulli effect, it exists the instrument.
The Flageolet was invented by Sieur Juvigny in the late 1500s. In more recent times it has been replaced by the tin whistle (or penny whistle).
Source: http://en.wikipedia.org/
Flageolet ébène
Source: http://en.wikipedia.org/wiki/File:Flageolet_%C3%A9b%C3%A8ne,_argent_et_nacre.JPG
Double flageolet
Source: http://www.miayf.org/woodwind/doubleflageolet/
The Double Flageolet was invented by William Bainbridge in the early 1800s.
http://www.flageolets.com/music/listen/