The characteristics of a scintillation counter - neon flash tube telescope have been investigated. The response of the scintillation counter and the efficiency of the neon flash tube trays for relativistic muons was measured. The equivalent characteristics for relativistic ⅓e and ⅔e quarks were evaluated from the above data. The efficiency of the telescope for detecting relativistic ⅓e and ⅔e quarks was thus obtained. The telescope was operated in a search for ⅓ and ⅔e quarks in cosmic rays at sea-level. The telescope was sensitive to ⅓e quarks in the β range 0.4 to 1.0 and to ⅔e quarks in the β range 0.8 to 1,0. In the running time obtained no quarks were detected. The rate of relativistic quarks is given with 90% confidence as: < 1.2.'. x 10(^-10) cm(^- 2) sterad (^-1) sec (^-1) for ⅓e quarks and <8.0 x 10(^-11) cm(^-2) sterad(^-1) sec(^-1) for ⅔e quarks. From these rates the upper limit of the production cross-section for quarks as a function of quark mass was evaluated and compared with theoretical predictions. The characteristics of a glass plate spark chamber and a stack of neon flash tubes operated in the localised discharge regime were investigated
