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A few years after the discovery of the cathode rays, i.e. 1886,Goldstein working a discharge tube with a perforated cathode and low pressure of about 1mm, noticed stream of luminosity at the back of the cathode,each stream proceeding away from the cathode. He called then canal rays,as they proceeded canalised by the holes in the cathode.
Properties:
1. They are streams of positive ions of the gas enclosed in the discharge tube.The mass of each ion is nearly equal to the mass of the gas atom.
2. They are deflected by electric and magnetic fields.Their deflection is opposite to that of cathode rays.
3. They travel in straight lines.
4. The velocity of canal rays is much smaller than the velocity of cathode rays.
5. They affect photographic plate.
6. They can penetrate through paper and thin foils of aluminium.
7. They cause fluorescence.
8. They ionise the gas through which they pass.