Positive rays are sometimes called as the canal waves. These were found by Goldstein. If the cathode of a discharged tube has holes in it and the pressure of the gas is around 10-3 mm of Hg then faint luminous glow comes out from every hole on the backside of the cathode. It is supposed positive pulses which are rolling out from the holes.     

Origin of positive rays: When potential dissimilarity is applied across the electrodes, electrons are gone from the cathode. As they move in the direction of anode, they gain power. These energetic electrons when hit with the atoms of the gas in the discharge tube, they ionize the atoms. The positive ions so formed at several places between cathode and anode travel towards the cathode. As during their motion, the positive ions when arrives the cathode, some pass by the holes in the cathode. These branches are the positive pulses.