1670 Picard (France) observed electrical discharge in a near-vacuum vessel. Read an explanation for this effect.
1705 Hauksbee (England) showed that the Picard effect was due to production of electric charges by friction.
1833 Faraday measured charge/mass ratios for ions in electrolysis.
1836 Faraday reported 'sparks, brushes, glows etc.' in different low pressure gases in discharge tubes.
1855 Geissler invented a mercury pump which made study of discharges at lower pressures possible.
1858 Plucker observed fluorescence in the wall of the discharge tube opposite the cathode at low pressure; after showing that the fluorescence could be moved around with a magnet, he concluded that it was due to currents of electricity flowing from the cathode.
1876 Goldstein used the term 'cathode rays' and thought they were some form of disturbance in the 'aether'.
1876 Varley, and later Crookes, constructed paddle-wheels on rails inside the discharge tubes and showed that the cathode rays could turn the paddle-wheels; Crookes changed the polarity of the electrodes to reverse the rotation of the wheel, concluding that the cathode rays had mass and velocity.
1893 Lenard began his work on cathode rays, starting with Hertz's observation that the rays could pass through thin metal plates. He was able to study the rays under simpler conditions than before. His work was considered to be important as a foundation for the subsequent identification of the electron as an elementary particle, and earnt him the 1905 Nobel prize.
1895 Perrin deflected cathode rays using a magnet.
1895 Hertz tried unsuccessfully to deflect cathode rays using an electric field.
Read about the ideas that developed in the latter half of the 19th century, as physicists, who had become deeply interested in the passage of electricity through gases, experimented, observed and drew conclusions.
1895 J.J.Thomson succeeded in deflecting cathode rays with both magnetic and electric fields, and calculated the charge/mass ratio of these negative particles. The charge/mass ratio of the cathode ray particles (electrons) was about 1000 times greater than the charge/mass ratio for Faraday's electrolysis ions. Did this mean the electrons had much higher charge or much less mass than the ions?
1900 Thomson was able to show that the negative charge of the electron was about the same size as the positive charge on a hydrogen ion.
Read several accounts of Thomson's work in his own words in several classic papers.
See how J.J.Thomson looked inside the atom at this American Institute of Physics page.
Thomson's Nobel prize was awarded in 1906.
1909 Millikan began a series of experiments leading to an accurate measurement of the charge of the electron.
Millikan's Nobel prize, awarded in 1923, recognized this work as well as his work on the photoelectric effect.
Further readings about the discovery of the electron.
Note that all the above observations were of electrons passing through gases.