The authors analyse the specific properties of the plasmascope as a device for investigating the processes which occur in a closed-end plasma chamber immersed in a magnetic field. They indicate its advantages and possibilities, and assess how much information can be obtained with it.The design elements of the plasmascope are described, together with certain techniques employed in its construction.The results are presented of plasmascope experiments with a low-temperature plasma obtained by means of gaseous discharge with an incandescent cathode. On the basis of these results it is possible to estimate the directed-motion velocities of the plasma, the plasma potential and the electric fields, and to obtain a picture of the instantaneous plasma density distribution over the transverse cross-section of the discharge. It is shown that the characteristic states of a discharge can be identified with the help of plasmagrams.