Abstract
By the method of coincidence of three Geiger-Müller tubes in line, cosmic ray observation is now in progress at Misima Observatory. Potential source is obtained by thermionic rectifier and condenser system, the fluctuation being controlled by the method of Street and Johnson. Coincidence is selected by the circuit proposed by Rossi and amplified with a thyratron TX930 to operate counter. In this preliminary note, we report mainly about some experiences of the Geiger-tube technique. It seems to us that the countvoltage characteristic is sensitively influenced by the inner surface condition of outside tube rather than the inner electrode. As for the actual counting due to cosmic radiation, we give only an example, as the sufficient data are not yet obtained.
