The passage of electricity through gases is possible if a high enough voltage is used, but it was discovered that at reduced pressure, conduction is much easier. The effect was studied by various scientists, Plücker (1858), Hittorf (1869), then Crookes (1879). The Crookes tube led to the observation that betwen 0.01 and 0.001 mm pressure a stream of rays is emitted from the cathode of the tube, these were called cathode rays. They were observed to travel in straight lines, generate shadows from objects placed in the evacuated tube, also to cause a small paddle wheel to rotate, and could be deflected by both electric and magnetic fields. J.J.Thompson proposed that they be called corpuscles, later electrons, they were apparently identical to the units of electricity found in solution. J.J. Thompson, in a seminal experiment, established rhe ratio of charge to mass of the electron, e/m. The mass, size and charge of the elctron were soon established by various experiments.