(General References [23 27])

In 1678 J. Picard noted a glow in the top of an agitated mercury barometer ("Picard's Glow"). Around 1720, F. Hawksbee used "frictional electricity" to generate a plasma in a vacuum that was intense enough "to read by." Scientists used "frictional electricity" to study the chemistry in electric sparks and plasmas before 1800. After the invention of the voltaic battery in 1800 by A. Volta, the study of the chemistry in electric arcs rapidly developed.

Since the mid-1800s there have been a number of studies of glow discharges and the spectral emission from the glows. The first glow (gas) discharge "vacuum tube" was made by M. Faraday in 1838 using brass electrodes and a vacuum of approximately 2 Torr. In 1857 Heinrich Geissler, who was the glassblower for Professor Julius Pl cker, invented the platinum-to-glass seal that allowed sealed-off glow-discharge tubes (Geissler tubes) to be produced. In 1860 J.H. Hittorf, a pupil of Plucker's, noted that "cathode rays" (electrons from the cathode) projected "shadows" in a gas discharge tube ( ^[E-7]). In 1885 Hittorf produced an externally excited plasma ("electrodeless ring discharge") by discharging a Leyden jar through a coil outside the glass chamber. W. Crookes made a number of studies using gas discharge tubes ("Crookes' tubes") ( ^[E-8]). Figure 4 shows a modern rendition of the Crookes' tube [27]. J.J. Thompson made a number of studies which indicated that the cathode ray was composed of negative particles that were the same as Stoney's "electrons." In...