The octagonal block of lead glass was observed by eight photomultiplier tubes. Four or five such counters, arranged in succession, were used on each arm of the bispectrometer in order to detect heavy particles of the same family as those observed at the Brookhaven and SLAC. They provided a means of identifying electrons. The arrangement of eight lateral photomultiplier tubes offered an efficient means of collecting the photons produced in the showers and determining, with a high resolution, the energy of the incident electrons. The total width at half-height was less than 6.9% foe electrons having an energy of 1 GeV.