Radioactivity and Atomic Structure

Abstract

William Morgan¹ found that an electrical discharge cannot be passed through the vacuum in a barometer tube over boiled mercury but does pass through an imperfect vacuum; he seems to have been the first to describe the discharge in a gas at very low pressure. Such discharges were first carefully investigated by Faraday (1837–8, see p. 127), but important progress was possible only after the invention of the mercury pump for producing higher vacua. This was done by Heinrich Geissler (1815–79), a glass-blower and mechanician in Bonn. He made Vacuum’ discharge tubes named after him, producing coloured and stratified discharges. Early in 1858 he showed a vacuum tube to Dr. W. H. T. Meyer, who described the mercury pump, the manufacture of vacuum tubes, and the influence of the magnetic field on the discharge.² That the conductivity of a gas is due to charged ions (atoms or molecules) was suggested by W. Giese,³ J. J. Thomson,⁴ and A. Schuster.⁵