Certain ancient stringed instruments were played with a plectrum or plucker made of the quill of a bird's feather, and the word has thus been used of a plectrum made of other material and differing in shape, and also of an analogous object for striking the strings in the harpsichord, spinet or virginal.
For the investigation of the spectra of gases at reduced pressures the so-called Plucker tubes (more generally but incorrectly called Geissler tubes) are in common use.
When, for instance, we observe the relation of the gas contained in a Plucker tube through which an electric discharge is passing, there can be little doubt that the partition of energy is very different from what it would be in thermal equilibrium.
(b) If a spark be sent through a Plucker tube containing hydrogen the lines are widened when the pressure 1 Trans.
According to circumstances, the colour of the light obtained from a Plucker vacuum tube changes "from red to a rich steel blue," to use the words of Crookes, who first described the phenomenon.